FePt-based sputtering target

ABSTRACT

An FePt-based sputtering target contains Fe, Pt, and a metal oxide, and further contains one or more kinds of metal elements other than Fe and Pt, wherein the FePt-based sputtering target has a structure in which an FePt-based alloy phase and a metal oxide phase containing unavoidable impurities are mutually dispersed, the FePt-based alloy phase containing Pt in an amount of 40 at % or more and less than 60 at % and the one or more kinds of metal elements in an amount of more than 0 at % and 20 at % or less with the balance being Fe and unavoidable impurities and with the total amount of Pt and the one or more kinds of metal elements being 60 at % or less, and wherein the metal oxide is contained in an amount of 20 vol % or more and 40 vol % or less based on the total amount of the target.

This is a Continuation of Application No. PCT/JP2013/050430 filed Jan.11, 2013, which claims the benefit of Japanese Application No.2012-005695 filed Jan. 13, 2012. The disclosure of the priorapplications is hereby incorporated by reference herein in its entirety.

TECHNICAL FIELD

The present invention relates to an FePt-based sputtering target and toa process for producing the same.

BACKGROUND ART

An FePt alloy can be provided with the fct (Ordered Face CenteredTetragonal) structure which has high crystal magnetic anisotropy byheat-treating at an elevated temperature (for example, at 600° C. orhigher), and therefore an FePt alloy has been highlighted as a magneticrecording medium. To make FePt particles smaller and more uniform in thethin film of the FePt alloy, it is proposed that a predeterminedquantity of carbon (C) be included into the thin film of the FePt alloy(for example, Patent Literature 1).

However, the formation method of the FePtC thin film, described in thePatent Literature 1, is the method of vapor-depositing Fe, Pt, and Csimultaneously on an MgO (100) substrate by using the Fe target of a2-inch diameter, C target of a 2-inch diameter, and the Pt target of 5mm in height and width. In this method, it is difficult to obtain thefilm whose composition is controlled strictly. Additionally, threetargets are required and each target needs a cathode, a power supply,etc, and so the cost of equipment becomes high while the preparatorywork of sputtering takes time and effort.

It is thought that an FePtC thin film formed by the process for formingan FePtC thin film described in Patent Literature 1 has a granularstructure in which FePt alloy particles are separated by partitions ofC, thereby allowing the FePtC thin film to exhibit magnetic recordingcharacteristics. However, when the partitions of the granular structurewere formed only of C (carbon), a carbon phase 14 grew to surround FePtalloy particles 12 growing on a substrate surface 10A of a substrate 10,for example, as illustrated in FIG. 1. This sometimes prevented the FePtalloy particles 12 from growing vertically onto the substrate surface10A so that a plurality of the FePt alloy particles 12 were depositedvertically onto the substrate surface 10A (for example, Non-PatentLiterature 1). When a plurality of the FePt alloy particles 12 aredeposited vertically onto the substrate surface 10A, the obtained thinfilm may have deteriorated characteristics as a magnetic recordingmedium, or may be useless as a magnetic recording medium.

In order to suppress the phenomenon that a plurality of the FePt alloyparticles 12 are deposited vertically onto the substrate surface 10A,metal oxides such as Ta₂O₅ and TiO₂ may be effectively used instead of Cto form the partitions of the granular structure, which is disclosed inNon-Patent Literature 1.

CITATION LIST Patent Literature

-   Patent Literature 1: Japanese Patent No. 3950838

Non-Patent Literature

-   Non-Patent Literature 1: J. S. Chen et al., Granular L1₀FePt—X (X═C,    TiO₂O₅) (001) nanocomposite films with small grain size for high    density magnetic recording, Journal of Applied Physics, American    Institute of Physics, 2009, Volume: 105, Pages: 07B702-1 to    07B702-3.

SUMMARY OF INVENTION Technical Problem

However, to form the partitions of the granular structure with a metaloxide instead of C, the process for firming an FePtC thin film describedin Patent Literature 1 requires installation of a metal oxide target,instead of a C target, into a sputtering device. This process takes timeand effort for preparation of sputtering and also increases the cost ofthe device.

The present inventors have believed that C and a metal oxide areeffectively used to form the partitions of the granular structure. Toform the partitions of the granular structure not with only C but with Cand a metal oxide, the process for forming an FePtC thin film describedin Patent Literature 1 not only requires installation of three targetsFe, Pt, and C into a sputtering device, but also requires installationof a metal, oxide target into a sputtering device. This process takesmore time and effort for preparation of sputtering and also increasesthe cost of the device.

The present inventors have studied about inclusion of a third metalelement in FePt-alloy particles to improve the performance of aFePt-based thin film as a magnetic recording medium and to improve theease of production. In order to include the third metal element in theFePt-alloy particles, the process for forming an FePtC thin filmdescribed in Patent Literature 1 further requires installation of atarget of the third metal element into a sputtering device. This processtakes more time and effort for preparation of sputtering and alsoincreases the cost of the device.

The present invention has been made in view of the aforementionedproblems. It is an object of the present invention to provide anFePt-based sputtering target which alone can form a thin film containingan FePt-based alloy and being usable as a magnetic recording mediumwithout using a plurality of targets, and a process for producing thesame.

Solution to Problem

As a result of intensive research to solve the aforementioned problem,the present inventors found out that the aforementioned problem issolvable with the following FePt-based sputtering targets and solvablewith the following processes for producing the FePt-based sputteringtarget, and the present inventors created the present invention.

Namely, a first aspect of an FePt-based sputtering target according tothe present invention is an FePt-based sputtering target containing Fe,Pt, a metal oxide, and further containing one or more kinds of metalelements other than Fe and Pt, wherein the FePt-based sputtering targethas a structure in which an FePt-based alloy phase and a metal oxidephase containing unavoidable impurities are mutually dispersed, theFePt-based alloy phase containing Pt in an amount of 40 at % or more andless than 60 at % and the one or more kinds of metal elements other thanFe and Pt in an amount of more than 0 at % and 20 at % or less with thebalance being Fe and unavoidable impurities and with a total amount ofPt and the one or more kinds of metal elements being 60 at % or less,and wherein the metal oxide is contained in an amount of 20 vol % ormore and 40 vol % or less based on a total amount of the target.

The phrase “an FePt-based alloy phase and a metal oxide phase containingunavoidable impurities are mutually dispersed” is a concept including astate in which the FePt-based alloy phase is a dispersion medium and themetal oxide phase is a dispersoid and a state in which the metal oxidephase is a dispersion medium and the FePt-based alloy phase is adispersoid and further including a state in which the FePt-based alloyphase and the metal oxide phase are mixed with each other but it is notpossible to determine which phase is a dispersion medium and which phaseis a dispersoid.

In the present description, the FePt-based alloy means an alloycontaining Fe and Pt as main components and includes not only a binaryalloy containing only Fe and Pt but also ternary and higher alloyscontaining Fe and Pt as main components and an additional metalelement(s) other than Fe and Pt. As used herein, the FePt-basedsputtering target means a sputtering target containing Fe and Pt as maincomponents and also includes sputtering targets containing, in additionto Fe and Pt, other metal component(s), an oxide, C, and the like.

In the present description, the phrase “α or more and β or less” may bedescribed as “from α to β.”

A second aspect of an FePt-based sputtering target according to thepresent invention is an FePt-based sputtering target containing Fe, Pt,C, a metal oxide, and further containing one or more kinds of metalelements other than Fe and Pt, wherein the FePt-based sputtering targethas a structure in which an FePt-based alloy phase, a C phase containingunavoidable impurities, and a metal oxide phase containing unavoidableimpurities are mutually dispersed, the FePt-based alloy phase containingPt in an amount of 40 at % or more and less than 60 at % and the one ormore kinds of metal elements other than Fe and Pt in an amount of morethan 0 at % and 20 at % or less with the balance being Fe andunavoidable impurities and with a total amount of Pt and the one or morekinds of metal elements being 60 at % or less, and wherein C iscontained in an amount of more than 0 vol % and 20 vol % or less basedon a total amount of the target, the metal oxide is contained in anamount of 10 vol % or more and less than 40 vol % based on the totalamount of the target, and a total content of C and the metal oxide is 20vol % or more and 40 vol % or less based on the total amount of thetarget.

The phrase “an FePt-based alloy phase, a C phase containing unavoidableimpurities, and a metal oxide phase containing unavoidable impuritiesare mutually dispersed” means a state in which any of the FePt-basedalloy phase, the C phase, and the metal oxide phase can be adispersoid(s) and any of the phases can be a dispersion medium/media,i.e., in any case, the FePt-based alloy phase, the C phase, and themetal oxide phase are mutually mixed, and moreover the above phrase is aconcept including a state in which the FePt-based alloy phase, the Cphase, and the metal oxide phase are mixed with each other but it is notpossible to determine which phase is a dispersion medium and which phaseis a dispersoid.

In the first aspect, the metal oxide phase preferably has an averagesize of 0.4 μm or less as determined by an intercept method.

In the second aspect, the phase consisting of the C phase and the metaloxide phase preferably has an average size of 0.4 μm or less asdetermined by an intercept method.

A process for determining the average size of the metal oxide phase bythe intercept method, and a process for determining the average size ofthe phase consisting of the C phase and the metal oxide phase will bedescribed below in the section of “DESCRIPTION OF EMBODIMENTS.”

In the first and second aspects, the one or more kinds of metal elementsother than Fe and Pt may be one or more kinds of Cu, Ag, Mn, Ni, Co, Pd,Cr, V. and B. The one or more metal elements other than Fe and Pt mayinclude Cu, or the one or more metal elements other than Fe and Pt maybe only Cu.

In the first and second aspects, the metal oxide may contain, forexample, at least one of SiO₂, TiO₂, Ti₂O₃, Ta₂O₅, Cr₂O₃, CoO, Co₃O₄,B₂O₃, CuO, Cu₂O, Y₂O₃, MgO, Al₂O₃, ZrO₂, Nb₂CO₅, MoO₃, CeO₂, Sm₂O₃,Gd₂O₃, WO₂, WO₃, HfO₂, and NiO₂.

Preferably, the FePt-based sputtering target has a relative density of90% or higher.

Some of the above-described FePt-based sputtering targets can bepreferably used for a magnetic recording medium.

A first aspect of a process for producing an FePt-based sputteringtarget according to the present invention is a process for producing anFePt-based sputtering target, including: adding metal oxide powdercontaining unavoidable impurities to FePt-based alloy powder containingPt in an amount of 40 at % or more and less than 60 at % and one or morekinds of metal elements other than Fe and Pt in an amount of more than 0at % and 20 at % or less with the balance being Fe and unavoidableimpurities and with a total amount of Pt and the one or more kinds ofmetal elements being 60 at % or less so that the metal oxide powderaccounts for 20 vol % or more and 40 vol % or less of a total amount ofthe FePt-based alloy powder and the metal oxide powder, followed bymixing the FePt-based alloy powder and the metal oxide powder to producea powder mixture; and molding the produced powder mixture while thepowder mixture is heated under pressure.

A second aspect of a process for producing an FePt-based sputteringtarget according to the present invention is a process for producing anFePt-based sputtering target, including: adding C powder containingunavoidable impurities and metal oxide powder containing unavoidableimpurities to FePt-based alloy powder containing Pt in an amount of 40at % or more and less than 60 at % and one or more kinds of metalelements other than Fe and Pt in an amount of more than 0 at % and 20 at% or less with the balance being Fe and unavoidable impurities and witha total amount of Pt and the one or more kinds of metal elements being60 at % or less so that the C powder and the metal oxide powder areadded to satisfy:0<α≦20;10≦β<40; and20≦α+β≦4.0,

where α and β represent contents of the C powder and the metal oxidepowder by vol %, respectively, based on a total amount of the FePt-basedalloy powder, the C powder, and the metal oxide powder, followed bymixing the FePt-based alloy powder, the C powder, and the metal oxidepowder to produce a powder mixture; and molding the produced powdermixture while the powder mixture is heated under pressure.

In a first aspect of the production process, the metal oxide phase inthe obtained FePt-based sputtering target has an average size of 0.4 μmor less as determined by the intercept method.

In a second aspect of the production process, the phase consisting ofthe C phase and the metal oxide phase in the obtained FePt-basedsputtering target has an average size of 0.4 μm or less as determined bythe intercept method.

In the first and second aspects of the production process, the one ormore kinds of metal elements other than Fe and Pt may be one or morekinds of Cu, Ag, Mn, Ni, Co, Pd, Cr, V, and B. The one or more metalelements other than Fe and Pt may include Cu, or the one or more metalelements other than Fe and Pt may be only Cu.

In the first and second aspects of the production process, the metaloxide may contain, for example, at least one of SiO₂, TiO₂, TiO₂, Ta₂O₅,Cr₂O₃, CoO, Co₃O₃, B₂O₃, Fe₂O₃, CuO, Cu₂O, Y₂O₃, MgO, Al₂O₃, ZrO₂,Nb₂O₃, MoO₃, CeO₂, Sm₂O₃, Gd₂O₃, WO₂, WO₃, HfO₂, and NiO₂.

Some of the obtained FePt-based sputtering targets can be preferablyused for a magnetic recording medium.

A third aspect of the FePt-based sputtering target according to thepresent invention is an FePt-based sputtering target produced by any oneof the above production processes.

Advantageous Effects of Invention

The use of the FePt-based sputtering target according to the presentinvention allows formation of a thin film containing an FePt-based alloyand being usable as a magnetic recording medium with the single targetalone, i.e., without using a plurality of targets.

Moreover, the FePt-based sputtering target according to the presentinvention contains a predetermined amount of the metal oxide, so that athin film obtained by sputtering and containing the FePt-based alloy islikely to have a favorable granular structure.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is an example of a problematic magnetic recording medium having agranular structure with partitions formed only of C (carbon).

FIG. 2 is a SEM photograph of a sintered product in Reference Example 1(an image taken at a magnification of 1,000×; a bar scale in thephotograph represents 10 μm).

FIG. 3 is a SEM photograph of a sintered product in Reference Example 1(an image taken at a magnification of 3,000×; a bar scale in thephotograph represents 1 μm).

FIG. 4 is a SEM photograph of a sintered product in Reference Example 1(an image taken at a magnification of 5,000×; a bar scale in thephotograph represents 1 μm).

FIG. 5 is a SEM photograph of a sintered product in Reference Example 1(an image taken at a magnification of 10,000×; a bar scale in thephotograph represents 1 μm).

FIG. 6 is a SEM photograph of a sintered product in Reference Example 2(an image taken at a magnification of 1,000×; a bar scale in thephotograph represents 10 μm).

FIG. 7 is a SEM photograph of a sintered product in Reference Example 2(an image taken at a magnification of 3,000×; a bar scale in thephotograph represents 1 μm).

FIG. 8 is a SEM photograph of a sintered product in Reference Example 2(an image taken at a magnification of 5,000×; a bar scale in thephotograph represents 1 μm).

FIG. 9 is a SEM photograph of a sintered product in Reference Example 2(an image taken at a magnification of 10,000×; a bar scale in thephotograph represents 1 μm).

FIG. 10 is a SEM photograph of a sintered product in Reference Example 3(an image taken at a magnification of 1,000×; a bar scale in thephotograph represents 10 μm).

FIG. 11 is a SEM photograph of a sintered product in Reference Example 3(an image taken at a magnification of 3,000×; a bar scale in thephotograph represents 1 μm).

FIG. 12 is a SEM photograph of a sintered product in Reference Example 3(an image taken at a magnification of 5,000×; a bar scale in thephotograph represents 1 μm).

FIG. 13 is a SEM photograph of a sintered product in Reference Example 3(an image taken at a magnification of 10,000×; a bar scale in thephotograph represents 1 μm).

FIG. 14 is a SEM photograph of a sintered product in Reference Example 4(an image taken at a magnification of 1,000×; a bar scale in thephotograph represents 10 μm).

FIG. 15 is a SEM photograph of a sintered product in Reference Example 4(an image taken at a magnification of 3,000×; a bar scale in thephotograph represents 1 μm).

FIG. 16 is a SEM photograph of a sintered product in Reference Example 4(an image taken at a magnification of 5,000×; a bar scale in thephotograph represents 1 μm).

FIG. 17 is a SEM photograph of a sintered product in Reference Example 4(an image taken at a magnification of 10,000×; a bar scale in thephotograph represents 1 μm).

FIG. 18 is a SEM photograph of a sintered product in Reference Example 5(an image taken at a magnification of 1,000×; a bar scale in thephotograph represents 10 μm).

FIG. 19 is a SEM photograph of a sintered product in Reference Example 5(an image taken at a magnification of 3,000×; a bar scale in thephotograph represents 1 μm).

FIG. 20 is a SEM photograph of a sintered product in Reference Example 5(an image taken at a magnification of 5,000×; a bar scale in thephotograph represents 1 μm).

FIG. 21 is a SEM photograph of a sintered product in Reference Example 5(an image taken at a magnification of 10,000×; a bar scale in thephotograph represents 1 μm).

FIG. 22 is a SEM photograph of a sintered product in Reference Example 6(an image taken at a magnification of 1,000×; a bar scale in thephotograph represents 10 μm).

FIG. 23 is a SEM photograph of a sintered product in Reference Example 6(an image taken at a magnification of 3,000×; a bar scale in thephotograph represents 1 μm).

FIG. 24 is a SEM photograph of a sintered product in Reference Example 6(an image taken at a magnification of 5,000×; a bar scale in thephotograph represents 1 μm).

FIG. 25 is a SEM photograph of a sintered product in Reference Example 6(an image taken at a magnification of 10,000×; a bar scale in thephotograph represents 1 μm).

FIG. 26 is a SEM photograph of a sintered product in Reference Example 7(an image taken at a magnification of 1,000×; a bar scale in thephotograph represents 10 μm).

FIG. 27 is a SEM photograph of a sintered product in Reference Example 7(an image taken at a magnification of 3,000×; a bar scale in thephotograph represents 1 μm).

FIG. 28 is a SEM photograph of a sintered product in Reference Example 7(an image taken at a magnification of 5,000×; a bar scale in thephotograph represents 1 μm).

FIG. 29 is a SEM photograph of a sintered product in Reference Example 7(an image taken at a magnification of 10,000×; a bar scale in thephotograph represents 1 μm).

FIG. 30 is a SEM photograph of a sintered product in Reference Example 8(an image taken at a magnification of 1,000×; a bar scale in thephotograph represents 10 μm).

FIG. 31 is a SEM photograph of a sintered product in Reference Example 8(an image taken at a magnification of 3,000×; a bar scale in thephotograph represents 1 μm).

FIG. 32 is a SEM photograph of a sintered product in Reference Example 8(an image taken at a magnification of 5,000×; a bar scale in thephotograph represents 1 μm).

FIG. 33 is a SEM photograph of a sintered product in Reference Example 8(an image taken at a magnification of 10,000×; a bar scale in thephotograph represents 1 μm).

FIG. 34 is a SEM photograph of a sintered product in Reference Example 9(an image taken at a magnification of 1,000×; a bar scale in thephotograph represents 10 μm).

FIG. 35 is a SEM photograph of a sintered product in Reference Example 9(an image taken at a magnification of 3,000×; a bar scale in thephotograph represents 1 μm).

FIG. 36 is a SEM photograph of a sintered product in Reference Example 9(an image taken at a magnification of 5,000×; a bar scale in thephotograph represents 1 μm).

FIG. 37 is a SEM photograph of a sintered product in Reference Example 9(an image taken at a magnification of 10,000×; a bar scale in thephotograph represents 1 μm).

FIG. 38 is a SEM photograph of a sintered product in Example 1 (an imagetaken at a magnification of 1,000×; a bar scale in the photographrepresents 10 μm).

FIG. 39 is a SEM photograph of a sintered product in Example 1 (an imagetaken at a magnification of 3,000×; a bar scale in the photographrepresents 1 μm).

FIG. 40 is a SEM photograph of a sintered product in Example 1 (an imagetaken at a magnification of 5,000×; a bar scale in the photographrepresents 1 μm).

FIG. 41 is a SEM photograph of a sintered product in Example 1 (an imagetaken at a magnification of 10,000×; a bar scale in the photographrepresents 1 μm).

FIG. 42 is a SEM photograph of a sintered product in Example 2 (an imagetaken at a magnification of 3,000×; a bar scale in the photographrepresents 1 μm).

FIG. 43 is a SEM photograph of a sintered product in Example 2 (an imagetaken at a magnification of 5.000×; a bar scale in the photographrepresents 1 μm).

FIG. 44 is a SEM photograph of a sintered product in Example 2 (an imagetaken at a magnification of 10,000×; a bar scale in the photographrepresents 1 μm).

DESCRIPTION OF EMBODIMENTS

Embodiments of the present invention will next be described in detail.

1. First Embodiment 1-1. Components and Structure of Sputtering Target

An FePt-based sputtering target according to a first embodiment of thepresent invention contains Fe, Pt, and a metal oxide and furthercontains Cu, which is a metal element other than Fe and Pt. TheFePt—C-based sputtering target is characterized in that it has astructure in which an FePt-based alloy phase and a metal oxide phasecontaining unavoidable impurities are mutually dispersed, the FePt-basedalloy phase containing Pt in an amount of 40 at % or more and less than60 at % and Cu in an amount of more than 0 at % and 20 at % or less withthe balance being Fe and unavoidable impurities and with the totalamount of Pt and Cu being 60 at % or less, and that the content of themetal oxide is 20 vol % or more and 40 vol % or less based on the totalamount of the target.

1-1-1. FePtCu Alloy

The FePt alloy can have an fct structure with high magnetocrystallineanisotropy when subjected to heat treatment at high temperature (e.g.,600° C. or higher). Therefore, the FePt alloy has a role in serving as arecording layer of a magnetic recording medium and is a main componentof the FePt-based sputtering target according to the first embodiment ofthe present invention. In the FePt-based sputtering target according tothe first embodiment, Cu is contained in an FePt alloy to form an FePtCualloy.

When Cu is contained, the temperature of the heat treatment forconverting the crystal structure of the FePt-based alloy to the fctstructure can be reduced (to, for example, 600° C.), so that the cost ofthe heat treatment on an FePtCu-metal oxide layer obtained by sputteringcan be reduced. In addition, the addition of Cu may allow the crystalstructure of the obtained FePtCu-metal oxide layer to be converted tothe fct structure by heat generated during sputtering without additionalheat treatment.

A metal other than Cu can be added to the FePt alloy, and examplesthereof include Ag, Mn, Ni, Co, Pd, Cr, V, and B.

In the first embodiment, the reason that the content of Pt in the FePtCualloy phase is defined to be 40 at % or more and less than 60 at % inthis embodiment is that, when the content of Pt in the FePtCu alloyphase is outside the range of 40 at % or more and less than 60 at %, thefct (ordered face centered tetragonal) structure may not appear. Thecontent of Pt in the FePtCu alloy phase is preferably 45 at % or moreand 55 at % or less, more preferably 49 at % or more and 51 at % orless, and particularly preferably 50 at %, from the viewpoint that thefct (ordered face centered tetragonal) structure appears reliably in theFePtCu alloy phase.

The reason that the content of Cu in the FePtCu alloy phase is definedto more than 0 at % and 20 at % or less is that the above-mentionedeffect of decreasing the temperature of the heat treatment (to, forexample, 600° C.) may not be obtained unless the FePtCu alloy phasecontains Cu, and that the proportion of Fe or Pt in the FePtCu alloyphase decreases if the FePtCu alloy phase contains more than 20 at % ofCu, so that the fct (ordered face centered tetragonal) structure may notappear.

The reason that the total amount of Pt and Cu in the FePtCu alloy phaseis defined to 60 at % or less is that the proportion of Fe in the FePtCualloy phase decreases if the total amount of Pt and Cu is more than 60at %, so that the fct (ordered face centered tetragonal) structure maynot appear.

1-1-2. Metal Oxide

The metal oxide can form the partitions for separating the FePtCu alloyparticles, which are magnetic particles, from each other in a layercontaining the FePtCu alloy and the metal oxide (hereinafter, may bereferred to as an FePtCu-metal oxide layer) obtained by sputtering, andhas a role in reducing and uniformizing the size of the FePtCu alloyparticles in the FePtCu-metal oxide layer. The metal oxide is a maincomponent in the FePtCu-based sputtering target according to the firstembodiment.

When only C is used instead of the metal oxide, C grows to surround theFePt-alloy particles during sputtering, as described above using FIG. 1.This may prevent the FePt-alloy particles from growing vertically ontothe substrate surface, so that the FePt-alloy particles may be depositedvertically onto the substrate surface to deteriorate the characteristicsas a magnetic recording medium. However, this can be avoided by usingthe metal oxide to obtain a favorable magnetic recording medium.

In the first embodiment, the reason that the content of the metal oxideis defined to 20 vol % or more and 40 vol % or less based on the totalamount of the target is that the metal oxide serves as partitions forseparating the FePtCu-alloy particles, which are magnetic particles,from each other in the FePtCu-metal oxide layer obtained by sputteringto achieve the effect of reducing and uniformizing the size of theFePtCu alloy particles. If the content of the metal oxide is less than20 vol %, this effect may not be sufficiently achieved. If the contentof the metal oxide exceeds 40 vol %, the number of the FePtCu alloyparticles per unit volume of the FePtCu-metal oxide layer obtained bysputtering decreases, and this is disadvantageous for storage capacity.The content of the metal oxide is preferably from 25 to 35 vol % basedon the total amount of the target, more preferably from 28 to 32 vol %,from the viewpoint of achieving the effect of reducing and uniformizingthe size of the FePtCu particles in the FePtCu-metal oxide layer andfrom the viewpoint of the storage capacity of the FePtCu-metal oxidelayer to be formed.

In the first embodiment, the metal oxide may contain, for example, atleast one of SiO₂, TiO₂, Ti₂O₃, Ta₂O₅, Cr₂O₃, CoO, Co₃O₄, B₂O₃, Fe₂O₃,CuO, Cu₂O, Y₂O₃, MgO, Al₂O₃, ZrO₂, Nb₂O₅, MoO₃, CeO₂, Sm₂O₃, Gd₂O₃, WO₂,WO₃, HfO₂, and NiO₂,

1-1-3. Structure of Target

The FePt-based sputtering target according to the first embodiment has astructure in which an FePtCu alloy phase and a metal oxide phasecontaining unavoidable impurities are mutually dispersed, the FePtCualloy phase containing Pt in an amount of 40 at % or more and less than60 at % and Cu in an amount of more than 0 at % and 20 at % or less withthe balance being Fe and unavoidable impurities and with the totalamount of Pt and Cu being 60 at % or less, wherein the content of themetal oxide is 20 vol % or more and 40 vol % or less based on the totalamount of the target.

The reason for having the structure in which the FePtCu alloy phase andthe metal oxide phase are mutually dispersed is to prevent certainregions from being sputtered at an excessive high rate during sputteringto improve the sputtering.

It is preferable to reduce the size of the metal oxide phase in thetarget as much as possible, in order to reduce the difference insputtering rate at different positions. Therefore, the average size ofthe metal oxide phase in the target is preferably 0.4 μm or less asdetermined by the intercept method, more preferably 0.35 μm or less, andparticularly preferably 0.3 μm or less.

In order to reduce the average size of the metal oxide phase in thetarget, the current size reduction technique requires extension of thetime for mixing FePtCu alloy powder and metal oxide powder. Therefore,it is unpractical to significantly reduce the average size of the metaloxide phase in the target with the current size reduction technique interms of production efficiency. When the average size of the metal oxidephase in the target is smaller to a certain extent, the problemassociated with the difference in sputtering rate at different positionsdoes not particularly occur. Therefore, the lower limit may be set onthe average size of the metal oxide phase in the target. When the lowerlimit is set, in consideration of the cost of the current size reductiontechnique, the average size of the metal oxide phase in the target, asdetermined by the intercept method, is preferably from 0.1 to 0.4 μm,more preferably from 0.15 to 0.35 μm, and particularly preferably from0.2 to 0.3 μm.

In the present description, the average size of the metal oxide phase isdetermined by the intercept method in the following manner.

First, two horizontal lines are drawn in a left-right direction on a SEMphotograph of the cross section of the target taken at a magnificationof 10,000× so that the image is divided vertically into three parts, andthree vertical lines are drawn in a vertical direction so that the imageis divided horizontally into four parts. As a result, a total of fivelines are drawn on the SEM photograph of the cross section of the targettaken at a magnification of 10,000×.

For each of the five lines, the total length of line segmentsintersecting the metal oxide phase and the number of the metal oxidephase intersected by the line are determined. Then the average of thelengths of the segments of the five lines that intersect the metal oxidephase is determined (by dividing the total length of the line segmentsintersecting the metal oxide phase by the number of the metal oxidephases intersected by the lines), and the obtained value is used as theaverage size of the metal oxide phase determined by the interceptmethod.

In order to perform sputtering favorably, it is preferable that therelative density of the target be large because the larger the value ofthe relative density, the smaller the volume of voids in the target.More specifically, the relative density of the target is preferably 90%,or higher. To increase the relative density of the target, it ispreferable to mix the FePtCu alloy powder and the metal oxide powdersufficiently to reduce the particle size of the metal oxide powder, asdescribed later. The size of the metal oxide phase in the target isthereby reduced, and the voids in the target can be filled by theplastic flow of the FePtCu alloy during sintering, so that the relativedensity increases.

The content of nitrogen is preferably 30 ppm by mass or less based onthe total amount of the target. As the content of nitrogen in the targetdecreases, the content of nitrogen in the FePtCu-metal oxide layer to beobtained by sputtering also decreases, so that the FePtCu-metal oxidelayer obtained is favorable.

1-2. Production Process

The FePt-based sputtering target according to the first embodiment canbe produced by: adding metal oxide powder containing unavoidableimpurities to FePtCu alloy powder containing Pt in an amount of 40 at %or more and less than 60 at % and Cu in an amount of more than 0 at %and 20 at % or less with the balance being Fe and unavoidable impuritiesand with the total amount of Pt and Cu being 60 at % or less, followedby mixing the FePtCu alloy powder and the metal oxide powder to producea powder mixture; and molding the produced powder mixture while thepowder mixture is heated under pressure.

In this production process, Fe, Pt and Cu are supplied as the FePtCualloy powder, and are not supplied as a single powder of Fe, a singlepowder of Pt, and a single powder of Cu. A single powder of Fe has highactivity and may ignite in the air. However, when Fe is alloyed with Ptand Cu to form an FePtCu alloy powder, the activity of Fe can be reducedeven in the form of powder. For this reason, this production process cansuppress oxidation and ignition of Fe during mixing with the metal oxidepowder, and/or oxidation and ignition of Fe when a mixing container isopen to the air after mixing.

When the atmosphere contains oxygen during the production of the powdermixture, it can prevent the metal oxide powder from being reduced duringmixing and thus can prevent incorporation of metal originated from themetal oxide powder into the FePtCu alloy powder during mixing.Therefore, an FePt-based thin film produced by using the obtainedFePt-based sputtering target is likely to exhibit stable magneticrecording characteristics.

1-2-1. Production of FePtCu Alloy Powder

No particular limitation is imposed on the process for producing theFePtCu alloy powder. However, in the first embodiment, an atomizingmethod is performed using a molten FePtCu alloy containing Pt in anamount of 40 at % or more and less than 60 at % and Cu in an amount ofmore than 0 at % and 20 at % or less with the balance being Fe andunavoidable impurities and with the total amount of Pt and Cu being 60at % or less to produce FePtCu alloy powder having the same compositionas the molten FePtCu alloy.

When the FePtCu alloy powder has the above composition, the FePtCu alloyphase in the target obtained by sintering of the FePtCu alloy powder hasthe above composition, so that the fct structure is likely to appear inan FePtCu phase in an FePtCu-metal oxide layer obtained by sputteringusing the above target.

Preferably, the FePtCu alloy powder is produced by an atomizing method.This is because of the following reason. In an atomizing method, rawmetals (Fe and Pt) are first heated to high temperature to form moltenmetals. In this stage, alkali metals such as Na and K, alkaline-earthmetals such as Ca, and gaseous impurities such as oxygen and nitrogenare volatilized and removed to the outside, so that the amount ofimpurities in the FePtCu alloy powder can be reduced. When a gasatomizing method is used, the amount of impurities in the FePtCu alloypowder can be further reduced by performing atomizing using argon gas ornitrogen gas.

The target obtained using the FePtCu alloy powder obtained by anatomizing method contains a reduced amount of impurities, so that thecontent of nitrogen can be suppressed to 30 mass ppm or less.

Therefore, sputtering performed using the target is favorable, and anFePtCu-metal oxide layer to be obtained is also favorable.

Examples of an applicable atomizing method include, for example, a gasatomizing method and a centrifugal atomizing method.

1-2-2. Mixing

The powder mixture is produced by mixing metal oxide powder having anaverage particle diameter of, for example, from 20 to 100 nm with theFePtCu alloy powder obtained by the atomizing method described above sothat the content of the metal oxide powder is 20 vol % or more and 40vol % or less based on the total amount of the powder mixture.

When the atmosphere contains oxygen during the production of the powdermixture, it can prevent the metal oxide powder from being reduced duringmixing and thus can prevent incorporation of metal originated from themetal oxide powder into the FePtCu alloy powder during mixing. AnFePt-based thin film produced by using the obtained FePt-basedsputtering target is likely to exhibit stable magnetic recordingcharacteristics.

From the viewpoint of preventing the metal oxide powder from beingreduced during mixing, it is preferable that oxygen be continuouslysupplied from the outside of the mixing container to the atmosphereduring mixing. Continuous supply of oxygen hardly causes a shortage ofoxygen in the atmosphere and easily prevents the metal oxide powder frombeing reduced during mixing.

However, if the amount of oxygen in the atmosphere during mixing of theFePtCu alloy powder and the metal oxide powder is too large, the powdermixture may contain an excess amount of oxygen during mixing.

From the viewpoint of preventing the metal oxide powder from beingreduced during mixing, and from the viewpoint that the powder mixturemay contain an excess amount of oxygen during mixing if the amount ofoxygen in the atmosphere is too large, the concentration of oxygen inthe atmosphere during mixing is preferably from 10 to 30 vol %, morepreferably from 15 to 25 vol %, particularly preferably from 19 to 22vol %.

Oxygen may be supplied to the atmosphere during mixing by supplying air.This can reduce cost.

The atmosphere during mixing may be composed substantially of an inertgas and oxygen. In this case, incorporation of impurities from theatmosphere into the powder mixture can be suppressed. For example,argon, nitrogen, etc. may be used as the inert gas.

The atmosphere during mixing may be released to the air at some point inthe mixing step. Even when the atmosphere is short of oxygen at somepoint in the mixing step, oxygen can be introduced from the air byreleasing the atmosphere into the air, so that the shortage of oxygencan be mitigated.

1-2-3. Molding Method

No particular limitation is imposed on the method for molding the powdermixture produced as described above while the powder mixture is heatedunder pressure. For example, a hot pressing method, a hot isostaticpressing method (HIP method), a spark plasma sintering method (SPSmethod), etc. may be used. Preferably, when implementing the presentinvention, such a molding method is performed in a vacuum or an inertgas atmosphere. In this case, even when the powder mixture contains acertain amount of oxygen (other than oxygen of the metal oxide), theamount of oxygen (other than oxygen of the metal oxide) in the obtainedsintered product decreases. The amount of impurities such as nitrogen inthe obtained sintered product also decreases.

1-3. Effects

When the target is produced by casting, it is difficult to increase thecontents of the metal oxide because of the solid solution limit of themetal oxide in the alloy, separation of the metal oxide from the alloydue to the difference in specific gravity, and the like.

Whereas, the production process in the first embodiment uses a sinteringmethod, and thus can increase the content of the metal oxide based onthe total amount of the target. More specifically, an FePt-basedsputtering target containing a large amount of the metal oxide, forexample, 20 vol % or more and 40 vol % or less, can be produced.Therefore, the use of the FePt-based sputtering target according to thefirst embodiment for spattering allows formation of a thin filmcontaining an FePt alloy and being usable as a magnetic recording mediumwith the single target alone, i.e., without using a plurality oftargets.

In the production process in the first embodiment, Fe is alloyed with Ptand Cu to form an FePtCu alloy powder, and thus the activity of Fe canbe reduced even in the form of powder, thereby suppressing ignition andoxidation of Fe during mixing with the metal oxide powder.

When the atmosphere contains oxygen during the production of the powdermixture, it can prevent the metal oxide powder from being reduced duringmixing and thus can prevent incorporation of metal originated from themetal oxide powder into the FePtCu alloy powder during mixing.Therefore, an FePt-based thin film produced by using the obtainedFePt-based sputtering target is likely to exhibit stable magneticrecording characteristics.

2. Second Embodiment

An FePt-based sputtering target according to a second embodiment will bedescribed below, but the description of the same content as in theFePt-based sputtering target according to the first embodiment will beappropriately omitted.

2-1. Components and Structure of Sputtering Target

The FePt-based sputtering target according to the first embodimentcontains a metal oxide in addition to alloy components (Fe, Pt, Cu);whereas the FePt-based sputtering target according to the secondembodiment contains C (carbon) and a metal oxide in addition to alloycomponents (Fe, Pt, Cu).

Specifically, the FePt-based sputtering target according to the secondembodiment of the present invention contains Fe, Pt, C, and a metaloxide, and further contains one or more kinds of metal elements otherthan Fe and Pt, wherein the FePt-based sputtering target has a structurein which an FePtCu alloy phase, a C phase containing unavoidableimpurities, and a metal oxide phase containing unavoidable impuritiesare mutually dispersed, the FePtCu alloy phase containing Pt in anamount of 40 at % or more and less than 60 at % and Cu in an amount ofmore than 0 at % and 20 at % or less with the balance being Fe andunavoidable impurities and with a total amount of Pt and Cu being 60 at% or less, and wherein the volume fraction of C to the total amount ofthe target is more than 0 vol % and 20 vol % or less, the volumefraction of the metal oxide to the total amount of the target is 10 vol% or more and less than 40 vol %, and the total volume fraction of C andthe metal oxide to the total amount of the target is 20 vol % or moreand 40 vol % or less.

2-1-1. FePtCu Alloy

In the FePt-based sputtering target according to the second embodimentof the present invention, Cu is contained in an FePt alloy to form anFePtCu alloy. The description of the FePtCu alloy in the FePt-basedsputtering target according to the second embodiment to be mentionedhere is overlapped with the content described in “1-1-1. FePtCu Alloy”in the first embodiment, and accordingly the description thereof will beomitted.

2-1-2. C and Metal Oxide

C and the metal oxide can form the partitions for separating the FePtCualloy particles, which are magnetic particles, from each other in alayer containing the FePtCu alloy, C, and the metal oxide (hereinafter,may be referred to as an FePtCu—C-metal oxide layer) obtained bysputtering, and has a role in reducing and uniformizing the size of theFePtCu alloy particles in the FePtCu—C-metal oxide layer. C and themetal oxide are main components in the FePt-based sputtering targetaccording to the second embodiment.

In the second embodiment, the content of C is more than 0 vol % and 20vol % or less based on the total amount of the target, the content ofthe metal oxide is 10 vol % or more and less than 40 vol % based on thetotal amount of the target, and the total content of C and the metaloxide is 20 vol % or more and 40 vol % or less based on the total amountof the target.

The reason that the content of C is set to more than 0 vol % and 20 vol% or less based on the total amount of the target, the content of themetal oxide is set to 10 vol % or more and less than 40 vol % based onthe total amount of the target, and the total content of C and the metaloxide is set to 20 vol % or more and 40 vol % or less based on the totalamount of the target is that C and the metal oxide can form thepartitions for separating the FePtCu alloy particles, which are magneticparticles, from each other in the FePtCu—C-metal oxide layer obtained bysputtering to achieve the effect of reducing and uniformizing the sizeof the FePtCu alloy particles. If the total content of C and the metaloxide is less than 20 vol %, this effect may not be sufficientlyachieved. If the total content of C and the metal oxide is more than 40vol %, the number of FePtCu alloy particles per unit volume of theFePtCu—C-metal oxide layer obtained by sputtering decreases, and this isdisadvantageous for storage capacity.

The reason that the lower limit of the content of the metal oxide is setto 10 vol % based on the total amount of the target and the upper limitof the content of C is set to 20 vol % based on the total amount of thetarget is that, when the target contains a large amount of C and aninsufficient amount of the metal oxide, C grows to surround the FePtCualloy particles during sputtering. This may prevent the FePt alloyparticles from growing vertically onto the substrate surface so that aplurality of the FePtCu alloy particles may be deposited vertically ontothe substrate surface to deteriorate the characteristics as a magneticrecording medium. This can be avoided by containing 10 vol % or more(less than 40 vol %) of the metal oxide based on the total amount of thetarget and setting the upper limit of the content of C to 20 vol % basedon the total amount of the target, making it possible to provide afavorable magnetic recording medium.

From the viewpoint of exhibiting the effect of reducing and uniformizingthe size of the FePtCu particles in the FePtCu—C-metal oxide layer, fromthe viewpoint of the storage capacity of the FePtCu—C-metal oxide layerto be formed, and from the viewpoint of providing favorablecharacteristics as a magnetic recording medium, the content of C ispreferably more than 0 vol % and 17 vol % or less based on the totalamount of the target, the content of the metal oxide is preferably 13vol % or more and less than 35 vol % based on the total amount of thetarget, and the total content of C and the metal oxide is preferably 25vol % or more and 35 vol % or less based on the total amount of thetarget.

In the second embodiment, the metal oxide may contain, for example, atleast one of SiO₂, TiO₂, Ti₂O₃, Ta₂O₅, Cr₂O₃, CoO, Co₃O₄, B₂O₃, Fe₂O₃,CuO, Cu₂O, Y₂O₃, MgO, Al₂O₃, ZrO₂, Nb₂O₅, MoO₃, CeO₂, Sm₂O₃, Gd₂O₃, WO₂,WO₃, HfO₂, and NiO₂.

2-1-3. Structure of Target

The FePt-based sputtering target according to the second embodiment hasa structure in which an FePtCu alloy phase, a C phase containingunavoidable impurities, and a metal oxide phase containing unavoidableimpurities are mutually dispersed, the FePtCu alloy phase containing Ptin an amount of 40 at % or more and less than 60 at % and Cu in anamount of more than 0 at % and 20 at % or less with the balance being Feand unavoidable impurities and with the total amount of Pt and Cu being60 at % or less, wherein the content of C is more than 0 vol % and 20vol % or less based on the total amount of the target, the content ofthe metal oxide is 10 vol % or more and less than 40 vol % based on thetotal amount of the target, and the total content of C and the metaloxide is 20 vol % or more and 40 vol % or less based on the total amountof the target.

The reason that the FePt-based sputtering target according to the secondembodiment has the structure in which the FePtCu alloy phase, the Cphase, and the metal oxide phase are mutually dispersed is to preventcertain regions from being sputtered at an excessive high rate duringsputtering to improve the sputtering.

It is preferable to reduce the size of the C phase and the metal oxidephase in the target as much as possible, in order to reduce thedifference in sputtering rate at different positions. Therefore, theaverage size of the phase consisting of the C phase and the metal oxidephase in the target is preferably 0.4 μm or less as determined by theintercept method, more preferably 0.35 μm or less, and particularlypreferably 0.3 μm or less.

In order to reduce the average size of the phase consisting of the Cphase and the metal oxide phase in the target, the current sizereduction technique requires extension of the time for mixing FePtCualloy powder, C powder, and metal oxide powder. Therefore, it isunpractical to significantly reduce the average size of the phaseconsisting of the C phase and the metal oxide phase in the target withthe current size reduction technique in terms of production efficiency.When the average size of the C phase and the metal oxide phase in thetarget is smaller to a certain extent, the problem associated with thedifference in sputtering rate at different positions does notparticularly occur. Therefore, the lower limit may be set on the averagesize of the C phase and the metal oxide phase in the target. When thelower limit is set, in consideration of the cost of the current sizereduction technique, the average size of the phase consisting of the Cphase and the metal oxide phase in the target, as determined by theintercept method, is preferably from 0.1 to 0.4 μm, more preferably from0.15 to 0.35 μm, and particularly preferably from 0.2 to 0.3 μm.

A process for determining the average size of the phase consisting ofthe C phase and the metal oxide phase by the intercept method is thesame as that described in the first embodiment except that the averagesize of the metal oxide phase is changed to the average size of thephase consisting of the C phase and the metal oxide phase, andaccordingly the description of the process will be omitted. As usedherein, the phase consisting of the C phase and the metal oxide phaserefers to a phase picked out as the C phase and the metal oxide phase,not distinguishing between the C phase and the metal oxide phase andregarding them as a same phase.

In order to perform sputtering favorably, it is preferable that therelative density of the target be large because the larger the value ofthe relative density, the smaller the volume of voids in the target.More specifically, the relative density of the target is preferably 90%or higher. To increase the relative density of the target, it ispreferable to mix the FePt alloy powder, the C powder, and the metaloxide powder sufficiently to reduce the particle size of the C powderand the metal oxide powder, as described later. The size of the C phaseand the metal oxide phase in the target is thereby reduced, and thevoids in the target can be filled by the plastic flow of the FePt alloyduring sintering, so that the relative density increases.

The content of nitrogen is preferably 30 ppm by mass or less based onthe total amount of the target. As the content of nitrogen in the targetdecreases, the content of nitrogen in the FePtCu—C-metal oxide layer tobe obtained by sputtering also decreases, so that the FePtCu—C-metaloxide layer obtained is favorable.

2-2. Production Process

The FePt-based sputtering target according to the second embodiment canbe produced by: adding C powder containing unavoidable impurities andmetal oxide powder containing unavoidable impurities to FePtCu alloypowder containing Pt in an amount of 40 at % or more and less than 60 at% and Cu in an amount of more than 0 at % and 20 at % or less with thebalance being Fe and unavoidable impurities and with the total amount ofPt and Cu being 60 at % or less, followed by mixing the FePtCu alloypowder, the C powder, and the metal oxide powder to produce a powdermixture; and molding the produced powder mixture while the powdermixture is heated under pressure.

In this production process, Fe, Pt, and Cu are supplied as the FePtCualloy powder in the same manner as in the production process in thefirst embodiment, and are not supplied as a single powder of Fe, asingle powder of Pt, and a single powder of Cu. A single powder of Fehas high activity and may ignite in the air. However, when Fe is alloyedwith Pt and Cu to form an FePtCu alloy powder, the activity of Fe can bereduced even in the form of powder. For this reason, this productionprocess can suppress oxidation and ignition of Fe during mixing with theC powder and metal oxide powder, and/or oxidation and ignition of Fewhen a mixing container is open to the air after mixing.

When the atmosphere contains oxygen during the production of the powdermixture, it can prevent the metal oxide powder from being reduced duringmixing and thus can prevent incorporation of metal originated from themetal oxide powder into the FePtCu alloy powder during mixing.Therefore, an FePt-based thin film produced by using the obtainedFePt-based sputtering target is likely to exhibit stable magneticrecording characteristics.

In the second embodiment, the powder mixture contains C powder. When theatmosphere contains oxygen during the production of the powder mixture,a certain amount of oxygen is adsorbed to the surface of the C powderduring mixing. Because a certain amount of oxygen has already beenadsorbed to the surface of C particles, rapid adsorption of oxygen tothe surface of the C particles and subsequent ignition of the Cparticles hardly occur even when a mixing container is opened tointroduce the air after mixing, thereby allowing stable production evenof the FePt-based sputtering target containing not only the metal oxidebut also C.

2-2-1. Production of FePtCu Alloy Powder

No particular limitation is imposed on the process for producing theFePtCu alloy powder. However, in this embodiment, an atomizing method isperformed using a molten FePtCu alloy containing Pt in an amount of 40at % or more and less than 60 at % and Cu in an amount of more than 0 at% and 20 at % or less with the balance being Fe and unavoidableimpurities and with the total amount of Pt and Cu being 60 at % or lessto produce FePtCu alloy powder having the same composition as the moltenalloy.

When the FePtCu alloy powder has the above composition, the FePtCu alloyphase in the target obtained by sintering of the FePtCu alloy powder hasthe above composition, so that the fct structure is likely to appear inan FePtCu phase in an FePtCu-metal oxide layer obtained by sputteringusing the above target.

In the second embodiment, the FePtCu alloy powder is produced by anatomizing method. This atomizing method is the same as the atomizingmethod in the production process in the first embodiment except that themolten alloy contains a predetermined amount of Cu, and accordingly thedescription of the atomizing method in the second embodiment will beomitted.

2-2-2. Mixing

The powder mixture is produced by mixing the FePt alloy powder obtainedby the atomizing method with the C powder having an average particlediameter of, for example, from 20 to 100 nm so that the content of C ismore than 0 vol % and 20 vol % or less based on the total amount of thepowder mixture, and further with the metal oxide powder having anaverage particle diameter of, for example, from 20 to 100 nm so that thecontent of the metal oxide is 10 vol % or more and less than 40 vol %based on the total amount of the powder mixture. The total content of Cand the metal oxide is 20 vol % or more and 40 vol % or less based onthe total amount of the powder mixture.

When the atmosphere contains oxygen during the production of the powdermixture, it can prevent the metal oxide powder from being reduced duringmixing and thus can prevent incorporation of metal originated from themetal oxide powder into the FePt alloy powder. An FePt-based thin filmproduced by using the obtained FePt-based sputtering target is likely toexhibit stable magnetic recording characteristics.

From the viewpoint of preventing the metal oxide powder from beingreduced during mixing, it is preferable that oxygen be continuouslysupplied from the outside of the mixing container to the atmosphereduring mixing. Continuous supply of oxygen hardly causes a shortage ofoxygen in the atmosphere and easily prevents the metal oxide powder frombeing reduced during mixing.

Also, from the viewpoint of avoiding ignition of the C particles evenwhen the mixing container is opened to introduce the air after mixing,it is preferable that oxygen be continuously supplied from the outsideof the mixing container to the atmosphere during mixing. When theatmosphere contains oxygen during the production of the powder mixture,a certain amount of oxygen has already been adsorbed to the surface ofthe C particles at the end of mixing. Therefore, rapid adsorption ofoxygen to the surface of the C particles and subsequent ignition of theC particles hardly occur even when a mixing container is opened tointroduce the air after mixing, thereby allowing stable production evenof the FePt-based sputtering target according to the second embodimentcontaining not only the metal oxide but also C.

However, if the amount of oxygen in the atmosphere during mixing of theFePt alloy powder and the metal oxide powder is too large, the powdermixture may contain an excess amount of oxygen during mixing and the Cparticles may ignite during mixing.

From the viewpoint of preventing the metal oxide powder from beingreduced during mixing, from the viewpoint of avoiding ignition of the Cparticles even when the mixing container is opened to introduce the airafter mixing, and from the viewpoint that the powder mixture may containan excess amount of oxygen during mixing and the C particles may igniteduring mixing if the amount of oxygen in the atmosphere is too large,the concentration of oxygen in the atmosphere during mixing ispreferably from 10 to 30 vol %, more preferably from 15 to 25 vol %,particularly preferably 19 to 22 vol %.

Oxygen may be supplied to the atmosphere during mixing by supplying air.This can reduce cost.

The atmosphere during mixing may be composed substantially of an inertgas and oxygen. In this case, incorporation of impurities from theatmosphere into the powder mixture can be suppressed. For example,argon, nitrogen, etc. may be used as the inert gas.

The atmosphere during mixing may be released to the air at some point inthe mixing step. Even when the atmosphere is short of oxygen at somepoint in the mixing step, oxygen can be introduced from the air byreleasing the atmosphere into the air, so that the shortage of oxygencan be mitigated.

2-2-3. Molding Method

A molding method in the second embodiment where the powder mixtureproduced as described above is molded while the powder mixture is heatedunder pressure is the same as the molding method in the productionprocess in the first embodiment, and accordingly the description of themolding method will be omitted.

2-3. Effects

When the target is produced by casting, it is difficult to increase thecontents of C and the metal oxide because of the solid solution limit ofC and the metal oxide in the alloy, separation of C and the metal oxidefrom the alloy due to the difference in specific gravity, and the like.

Whereas, the production process in the second embodiment uses asintering method and thus can increase the contents of C and the metaloxide based on the total amount of the target, making it possible toproduce an FePt-based sputtering target in which the content of C ismore than 0 vol % and 20 vol % or less based on the total amount of thetarget, the content of the metal oxide is 10 vol % or more and less than40 vol % based on the total amount of the target, and the total contentof C and the metal oxide is 20 vol % or more and 40 vol % or less basedon the total amount of the target. Therefore, the use of the FePt-basedsputtering target according to the second embodiment for spatteringallows formation of a thin film containing an FePt-based alloy and beingusable as a magnetic recording medium with the single target alone,i.e., without using a plurality of targets.

In the production process in the second embodiment, Fe is alloyed withPt and Cu to form an FePtCu alloy powder in the same manner as in theproduction process of the first embodiment, and thus the activity of Fecan be reduced even in the form of powder, thereby suppressing ignitionand oxidation of Fe during mixing with the C powder the metal oxidepowder.

When the atmosphere contains oxygen during the production of the powdermixture, it can prevent the metal oxide powder from being reduced duringmixing and thus can prevent incorporation of metal originated from themetal oxide powder into the FePtCu alloy powder during mixing.Therefore, an FePt-based thin film produced by using the obtainedFePt-based sputtering target is likely to exhibit stable magneticrecording characteristics.

In the production process in the second embodiment, C powder is alsoused, and when the atmosphere contains oxygen during the production ofthe powder mixture, a certain amount of oxygen is adsorbed to thesurface of the C powder during mixing. Because a certain amount ofoxygen has already been adsorbed to the surface of the C particles,rapid adsorption of oxygen to the surface of the C particles andsubsequent ignition of the C particles hardly occur even when the mixingcontainer is opened to introduce the air after mixing, thereby allowingstable production even of the FePt-based sputtering target according tothe second embodiment containing not only the metal oxide but also C.

EXAMPLES Reference Example 1

The targeted composition of a powder mixture and a target in ReferenceExample 1 is (50Fe-50Pt)-30 vol % SiO₂. More specifically, the targetedcomposition of the metal components is 50 at % Fe-50 at % Pt, and thetargeted content of the metal oxide (SiO₂) is 30 vol % based on thetotal amount of the target. When the content of the metal oxide (SiO₂)is represented not by vol % but by mol %, the targeted composition ofthe powder mixture and the target in Reference Example 1 is(50Fe-50Pt)-11.27 mol % SiO₂.

The metals in bulk form were weighed such that the composition of thealloy was Fe: 50 at % and Pt: 50 at % and then heated by high frequencyheating to form a molten Fe—Pt alloy at 1,800° C. Then a gas atomizingmethod using argon gas was performed to produce 50 at % Fe-50 at % Ptalloy powder. The average particle diameter of the obtained alloy powderwas measured using Microtrac MT3000 manufactured by NIKKISO Co., Ltd.and found to be 50 μm.

66.91 g of SiO₂ powder having an average particle diameter of 0.7 μm anda bulk density of 2.20 g/cm³ was added to 1100.00 g of the obtained 50at % Fe-50 at % Pt alloy powder such that the content of SiO₂ was 30 vol% based on the total amount of the powders, and then these componentswere mixed using a ball mill until the cumulative number of revolutionsreached 3,741,120 to thereby produce a powder mixture. Hereinafter, thecumulative number of revolutions of the ball mill may be referred to asthe cumulative number of ball mill revolutions or simply as the numberof revolutions.

During mixing, the mixing container was hermetically closed with a lidand filled with a gas mixture (Ar+O₂), and under the atmosphere in themixing container, the 50 at % Fe-50 at % Pt alloy powder and SiO₂ powderwere mixed.

When the cumulative number of ball mill revolutions reached 935,280,1,870,560, 2,805,840 and 3,741,120, the mixing container was opened, andwhether or not ignition had occurred was visually checked. However, noignition was found at each point.

When the cumulative number of ball mill revolutions reached 1,870,560,2,805,840, and 3,741,120, 30.00 g of the powder mixtures were subjectedto hot pressing in a vacuum atmosphere at less than 20 Pa to producedisc-like sintered products having a diameter of 30 mm. The hot-pressingconditions (sintering temperature, sintering pressure, and sinteringtime) and the relative densities of the obtained sintered products areshown in TABLE 1 below. The theoretical density of the sintered productis 11.51 g/cm³.

TABLE 1 Cumulative Relative number of Hot-pressure conditions density ofball mill Sintering Sintering Sintering sintered revolutions temperaturepressure time product (Number) (° C.) (MPa) (min) (%) Ignition 935,280 —— — — — 1,870,560 1070 26.2 45 96.96 NO 2,805,840 1070 26.2 45 97.03 NO3,741,120 1050 26.2 45 98.61 NO

The relative densities of the sintered products exceed 96%, and theamount of voids in the obtained sintered products was small.

The contents of oxygen and nitrogen in the powder mixture taken at acumulative number of ball mill revolutions of 3,741,120 were measuredusing a TC-600 Series Nitrogen/Oxygen Determinator manufactured by LECOCorporation. The contents of oxygen and nitrogen in the sintered productmade using the powder mixture taken at a cumulative number of ball millrevolutions of 3,741,120 were measured using a TC-600 SeriesNitrogen/Oxygen Determinator manufactured by LECO Corporation. Themeasurement results are shown in TABLE 2 below.

TABLE 2 Cumulative number of ball mill revolutions Oxygen Nitrogen of3,741,120 (mass %) (mass ppm) Powder mixture 3.36 42 Sintered product3.21 19

The content of oxygen and the content of nitrogen in the sinteredproduct both decrease compared to those in the powder mixture, while thedegree of reduction in the content of oxygen is smaller than the degreeof reduction in the content of nitrogen. This may be caused by the factthat the powder mixture and the sintered product both contain metaloxide SiO₂.

The structure of the sintered product made using the powder mixturetaken at a cumulative number of ball mill revolutions of 3,741,120 wasobserved under a scanning electron microscope (SEM). FIGS. 2 to 5 showSEM photographs of the sintered products. FIG. 2 is a SEM photographtaken at a magnification of 1,000× (a bar scale in the photographrepresents 10 μm). FIG. 3 is a SEM photograph taken at a magnificationof 3,000× (a bar scale in the photograph represents 1 μm). FIG. 4 is aSEM photograph taken at a magnification of 5,000× (a bar scale in thephotograph represents 1 μm). FIG. 5 is a SEM photograph taken at amagnification of 10,000× (a bar scale in the photograph represents 1μm). In FIGS. 2 to 5, black portions correspond to the SiO₂ phase, andwhite portions correspond to the FePt alloy phase. As can be seen fromFIGS. 2 to 5, fine regions of the SiO₂ phase are dispersed in the entirearea of the structure.

The average size of the SiO₂ phase was determined by the interceptmethod based on the SEM photograph of FIG. 5 taken at a magnification of10,000×.

Specifically, two horizontal lines were drawn in a left-right directionon the SEM photograph of FIG. 5 so that the image was divided verticallyinto three parts, and three vertical lines were drawn in a verticaldirection so that the image was divided horizontally into four parts.Thus, a total of five lines are drawn on the SEM photograph of FIG. 5.

For each of the five lines, the total length of line segmentsintersecting the SiO₂ phase and the number of the SiO₂ phase intersectedby the line were determined. Then the average of the lengths of thesegments of the five lines that intersected the SiO₂ phase wasdetermined (by dividing the total length of the line segmentsintersecting the SiO₂ phase by the number of the SiO₂ phases intersectedby the lines), and the obtained value was used as the average size ofthe SiO₂ phase determined by the intercept method. The results showedthat the average size of the SiO₂ phase determined by the interceptmethod was 0.34 μm.

Reference Example 2

The targeted composition of a powder mixture and a target in ReferenceExample 2 is (50Fe-50Pt)-30 vol % TiO₂. More specifically, the targetedcomposition of the metal components is 50 at % Fe-50 at % Pt, and thetargeted content of the metal oxide (TiO₂) is 30 vol % based on thetotal amount of the target. When the content of the metal oxide (TiO₂)is represented not by vol % but by mol %, the targeted composition ofthe powder mixture and the target in Reference Example 2 is(50Fe-50Pt)-15.34 mol % TiO₂.

To 1100.00 g of 50 at % Fe-50 at % Pt alloy powder produced in the samemanner as in Reference Example 1, 126.85 g of TiO₂ powder having anaverage particle diameter of 0.07 μm and a bulk density of 4.11 g/cm³was added so that the content of TiO₂ was 30 vol % based on the totalamount of the powders. These components were then mixed with a ball milluntil the cumulative number of revolutions reached 3,741,120 to producea powder mixture.

During mixing, the mixing container was hermetically closed with a lidand filled with a gas mixture (Ar+O₂), and under the atmosphere in themixing container, the 50 at % Fe-50 at % Pt alloy powder and TiO₂ powderwere mixed.

When the cumulative number of ball mill revolutions reached 935,280,1,870,560, 2,805,840 and 3,741,120, the mixing container was opened, andwhether or not ignition had occurred was visually checked. However, noignition was found at each point.

When the cumulative number of ball mill revolutions reached 1,870,560,2,805,840, and 3,741,120, 30.00 g of the powder mixtures were subjectedto hot pressing in a vacuum atmosphere at less than 20 Pa to producedisc-like sintered products having a diameter of 30 mm. The hot-pressingconditions (sintering temperature, sintering pressure, and sinteringtime) and the relative densities of the obtained sintered products areshown in TABLE 3 below. The theoretical density of the sintered productis 12.10 g/cm³.

TABLE 3 Cumulative Relative number of Hot-pressure conditions density ofball mill Sintering Sintering Sintering sintered revolutions temperaturepressure time product (Number) (° C.) (MPa) (min) (%) Ignition 935,280 —— — — — 1,870,560 1000 26.2 45 97.54 NO 2,805,840 960 26.2 45 96.97 NO3,741,120 950 26.2 45 96.69 NO

The relative densities of the sintered products exceed 96%, and theamount of voids in the obtained sintered products was small.

The contents of oxygen and nitrogen in the powder mixture taken at acumulative number of ball mill revolutions of 3,741,120 were measuredusing a TC-600 Series Nitrogen/Oxygen Determinator manufactured by LECOCorporation. The contents of oxygen and nitrogen in the sintered productmade using the powder mixture taken at a cumulative number of ball millrevolutions of 3,741,120 were measured using a TC-600 SeriesNitrogen/Oxygen Determinator manufactured by LECO Corporation. Themeasurement results are shown in TABLE 4 below.

TABLE 4 Cumulative number of ball mill revolutions Oxygen Nitrogen of3,741,120 (mass %) (mass ppm) Powder mixture 4.52 46 Sintered product3.96 31

The content of oxygen and the content of nitrogen in the sinteredproduct both decrease compared to those in the powder mixture, while thedegree of reduction in the content of oxygen is smaller than the degreeof reduction in the content of nitrogen. This may be caused by the factthat the powder mixture and the sintered product both contain metaloxide TiO₂.

The structure of the sintered product made using the powder mixturetaken at a cumulative number of ball mill revolutions of 3,741,120 wasobserved under a scanning electron microscope (SEM). FIGS. 6 to 9 showSEM photographs of the sintered products. FIG. 6 is a SEM photographtaken at a magnification of 1,000× (a bar scale in the photographrepresents 10 μm). FIG. 7 is a SEM photograph taken at a magnificationof 3,000× (a bar scale in the photograph represents 1 μm). FIG. 8 is aSEM photograph taken at a magnification of 5,000× (a bar scale in thephotograph represents 1 μm). FIG. 9 is a SEM photograph taken at amagnification of 10,000× (a bar scale in the photograph represents 1μm). In FIGS. 6 to 9, black portions correspond to the TiO₂ phase, andwhite portions correspond to the FePt alloy phase. As can be seen fromFIGS. 6 to 9, fine regions of the TiO₂ phase are dispersed in the entirearea of the structure.

The average size of the TiO₂ phase was determined by the interceptmethod based on the SEM photograph of FIG. 9 taken at a magnification of11,000×. A specific method is the same as the method of ReferenceExample 1.

The results showed that the average size of the TiO₂ phase determined bythe intercept method was 0.28 μm.

Reference Example 3

The targeted composition of a powder mixture and a target in ReferenceExample 3 is (50Fe-50Pt)-36.63 vol % B₂O₃. More specifically, thetargeted composition of the metal components is 50 at % Fe-50 at % Pt,and the targeted content of the metal oxide (B₂O₃) is 36.63 vol % basedon the total amount of the target. When the content of the metal oxide(B₂O₃) is represented not by vol % but by mol %, the targetedcomposition of the powder mixture and the target in Reference Example 3is (50Fe-50Pt)-11 mol % B₂O₃.

To 1100.00 g of 50 at % Fe-50 at % Pt alloy powder produced in the samemanner as in Reference Example 1, 75.44 g of B₂O₃ powder was added sothat the content of B₂O₃ was 36.63 vol % based on the total amount ofthe powders. These components were then mixed with a ball mill until thecumulative number of revolutions reached 5,736,960 to produce a powdermixture.

During mixing, the mixing container was hermetically closed with a lidand filled with a gas mixture (Ar+O₂), and under the atmosphere in themixing container, the 50 at % Fe-50 at % Pt alloy powder and B₂O₃ powderwere mixed.

When the cumulative number of ball mill revolutions reached 935,280,2,535,840, 4,136,400 and 5,736,960, the mixing container was opened, andwhether or not ignition had occurred was visually checked. However, noignition was found at each point.

When the cumulative number of ball mill revolutions reached 4,136,400and 5,736,960, 30.00 g of the powder mixtures were subjected to hotpressing in a vacuum atmosphere at less than 20 Pa to produce disc-likesintered products having a diameter of 30 mm. The hot-pressingconditions (sintering temperature, sintering pressure, and sinteringtime) and the relative densities of the obtained sintered products areshown in TABLE 5 below. The theoretical density of the sintered productis 10.50 g/cm³. According to calculation based on the theoreticaldensity of this sintered product of 10.50 g/cm³, the relative densitiesof the sintered products were 103.95% (cumulative number of ball millrevolutions: 4,136,400) and 105.22% (cumulative number of ball millrevolutions: 5,736,960) as shown in TABLE 5 below.

TABLE 5 Cumulative Relative number of Hot-pressure conditions density ofball mill Sintering Sintering Sintering sintered revolutions temperaturepressure time product (Number) (° C.) (MPa) (min) (%) Ignition 935,280 —— — — NO 2,535,840 — — — — NO 4,136,400 810 26.2 45 103.95 NO 5,736,960840 26.2 45 105.22 NO

The relative density of the sintered product is 105.22%, or over 100%,and the amount of voids in the obtained sintered products was small.

The contents of oxygen and nitrogen in the sintered product made usingthe powder mixture taken at a cumulative number of ball mill revolutionsof 5,736,960 were measured using a TC-600 Series Nitrogen/OxygenDeterminator manufactured by LECO Corporation. The measurement resultsare shown in TABLE 6 below.

TABLE 6 Cumulative number of ball mill revolutions Oxygen Nitrogen of5,736,960 (mass %) (mass ppm) Sintered product 4.86 35

The contents of Fe, Pt, and B in the sintered product made of the powdermixture taken at a cumulative number of ball mill revolutions of5,736,960 were analyzed by ICP. TABLE 7 below shows the analysis resultsas well as the contents of Fe, Pt, and B in the powder mixture beforesintering. The contents of Fe, Pt, and B in the powder mixture beforesintering are not the analysis results by ICP but the calculated values(theoretical values) based on the amounts of raw material powdersblended for producing the powder mixture.

TABLE 7 Cumulative number of ball mill revolutions Fe Pt B of 5,736,960(mass %) (mass %) (mass %) Powder mixture 20.83 72.75 1.99 Sinteredproduct 19.76 72.99 2.02

The structure of the sintered product made using the powder mixturetaken at a cumulative number of ball mill revolutions of 5,736,960 wasobserved under a scanning electron microscope (SEM). FIGS. 10 to 13 showSEM photographs of the sintered products. FIG. 10 is a SEM photographtaken at a magnification of 1,000× (a bar scale in the photographrepresents 10 μm). FIG. 11 is a SEM photograph taken at a magnificationof 3,000× (a bar scale in the photograph represents 1 μm). FIG. 12 is aSEM photograph taken at a magnification of 5,900× (a bar scale in thephotograph represents 1 μm). FIG. 13 is a SEM photograph taken at amagnification of 10,000× (a bar scale in the photograph represents 1μm). In FIGS. 10 to 13, black portions correspond to the B₂O₃ phase, andgray portions correspond to the FePt alloy phase. As can be seen fromFIGS. 10 to 13, fine regions of the B₂O₃ phase are dispersed in theentire area of the structure.

The average size of the B₂O₃ phase was determined by the interceptmethod based on the SEM photograph of FIG. 13 taken at a magnificationof 10,000×. A specific method is the same as the method of ReferenceExample 1.

The results showed that the average size of the B₂O₃ phase determined bythe intercept method was 0.22 μm.

Reference Example 4

The targeted composition of a powder mixture and a target in ReferenceExample 4 is (50Fe-50Pt)-12.07 vol % B₂O₃-24.68 vol % SiO₂. That is, thetargeted composition of metal components is 50 at % Fe-50 at % Pt; thetargeted content of metal oxide B₂O₃ is 12.07 vol % based on the totalamount of the target; and the targeted content of metal oxide SiO₂ is24.68 vol % based on the total amount of the target. When the contentsof B₂O₃ and SiO₂ are represented not by vol % but by mol %, the targetedcomposition of the powder mixture and the target in Reference Example 4is (50Fe-50Pt)-3.53 mol % BO 3-10 mol % SiO₂.

To 970.00 g of 50 at % Fe-50 at % Pt alloy powder produced in the samemanner as in Reference Example 1, 21.97 g of B₂O₃ powder was added sothat the content of B₂O₃ is 12.07 vol % based on the total amount of thepowders, and 53.72 g of SiO₂ powder having an average particle diameterof 0.7 μm and a bulk density of 2.20 g/cm³ was added so that the contentof SiO₂ was 24.68 vol % based on the total amount of the powders. Thesecomponents were then mixed with a ball mill until the cumulative numberof revolutions reached 3,852,360 to produce a powder mixture.

During mixing, the mixing container was hermetically closed with a lidand filled with a gas mixture (Ar+O₂); and under the atmosphere in themixing container, the 50 at % Fe-50 at % Pt alloy powder, the B₂O₃powder, and the SiO₂ powder were mixed.

When the cumulative number of ball mill revolutions reached 1,046,520,1,981,800, 2,917,080 and 3,852,360, the mixing container was opened, andwhether or not ignition had occurred was visually checked. However, noignition was found at each point.

When the cumulative number of ball mill revolution reached 3,852,360,30.00 g of the powder mixture was subjected to hot pressing in a vacuumatmosphere at less than 20 Pa to produce a disc-like sintered producthaving a diameter of 30 mm. The hot-pressing conditions (sinteringtemperature, sintering pressure, and sintering time) and the relativedensity of the obtained sintered product are shown in TABLE 8 below. Ifthere is no difference between the amounts of B and Si contained in thepowder mixture before sintering and those contained in the sinteredproduct after sintering, the theoretical density of the sintered productis 10.57 g/cm³. As a result of the analysis of the sintered product byICP, the content of B decreased by 0.01% by mass compared to the powdermixture before sintering, and the content of Si decreased by 0.04% bymass compared to the powder mixture before sintering (see, TABLE 10).Considering this and assuming that all B in the sintered product wasB₂O₃ and all Si in the sintered product was SiO₂, the theoreticaldensity of the sintered product was calculated and found to be 10.59g/cm³. Based on the theoretical density of this sintered product of10.59 g/cm³, the relative density of the sintered product was calculatedand found to be 100.38% as shown in TABLE 8 below.

TABLE 8 Cumulative Relative number of Hot-pressure conditions density ofball mill Sintering Sintering Sintering sintered revolutions temperaturepressure time product (Number) (° C.) (MPa) (min) (%) Ignition 1,046,520— — — — NO 1,981,800 — — — — NO 2,917,080 — — — — NO 3,852,360 830 26.245 100.38 NO

The relative density of the sintered product was about 100%, and theamount of voids in the obtained sintered product was small. The relativedensity of the sintered product shown in TABLE 8 above is 100.38%, orover 100%. This is regarded as measurement error.

The contents of oxygen and nitrogen in the sintered product made usingthe powder mixture taken at a cumulative number of ball mill revolutionsof 3,852,360 were measured using a TC-600 Series Nitrogen/OxygenDeterminator manufactured by LECO Corporation. The measurement resultsare shown in TABLE 9 below.

TABLE 9 Cumulative number of ball mill revolutions Oxygen Nitrogen of3,852,360 (mass %) (mass ppm) Sintered product 4.19 25

The contents of Fe, Pt, B, and Si in the sintered product made of thepowder mixture taken at a cumulative number of ball mill revolutions of3,852,360 were analyzed by ICP. TABLE 10 below shows the analysisresults as well as the contents of Fe, Pt, B, and Si in the powdermixture before sintering.

TABLE 10 Cumulative number of ball mill revolutions Fe Pt B Si of3,852,360 (mass %) (mass %) (mass %) (mass %) Powder mixture 20.64 72.120.65 2.40 Sintered product 21.24 71.67 0.64 2.36

The structure of the sintered product made using the powder mixturetaken at a cumulative number of ball mill revolutions of 3,852,360 wasobserved under a scanning electron microscope (SEM). FIGS. 14 to 17 showSEM photographs of the sintered products. FIG. 14 is a SEM photographtaken at a magnification of 1,000× (a bar scale in the photographrepresents 10 μm). FIG. 15 is a SEM photograph taken at a magnificationof 3,000× (a bar scale in the photograph represents 1 μm). FIG. 16 is aSEM photograph taken at a magnification of 5,000× (a bar scale in thephotograph represents 1 μm). FIG. 17 is a SEM photograph taken at amagnification of 10,000× (a bar scale in the photograph represents 1μm). In FIGS. 14 to 17, black portions correspond to the metal oxidephase (the B₂O₃ phase and the SiO₂ phase), and gray portions correspondto the FePt alloy phase. As can be seen from FIGS. 14 to 17, fineregions of the metal oxide phase (the B₂O₃ phase and the SiO₂ phase) aredispersed in the entire area of the structure.

The average size of the metal oxide phase (the phase consisting of theB₂O₃ phase and the SiO₂ phase) was determined by the intercept methodbased on the SEM photograph of FIG. 17 taken at a magnification of10,000×. A specific method is the same as the method of ReferenceExample 1.

The results showed that the average size of the metal oxide phase (thephase consisting of the B₂O₃ phase and the SiO₂ phase) determined by theintercept method was 0.27 μm.

Reference Example 5

The targeted composition of a powder mixture and a target in ReferenceExample 5 is (50Fe-50Pt)-6 vol % C-24 vol % SiO₂. That is, the targetedcomposition of metal components is 50 at % Fe-50 at % Pt; the targetedcontent of C is 6 vol % based on the total amount of the target; and thetargeted content of metal oxide (SiO₂) is 24 vol % based on the totalamount of the target. When the contents of C and metal oxide (SiO₂) arerepresented not by vol % but by mol %, the targeted composition of thepowder mixture and the target in Reference Example 5 is(50Fe-50Pt)-10.60 mol % C-8.25 mol % SiO₂.

To 1100.00 g of 50 at % Fe-50 at % Pt alloy powder produced in the samemanner as in Reference Example 1, 13.72 g of C powder having an averageparticle diameter of 35 m and a bulk density of 0.25 g/cm³ was added sothat the content of C is 5.7 vol % based on the total amount of thepowders, and 53.44 g of SiO₂ powder having an average particle diameterof 0.7 μm and a bulk density of 2.20 g/cm³ was added so that the contentof SiO₂ was 23.4 vol % based on the total amount of the powders. Thesecomponents were then mixed with a ball mill until the cumulative numberof revolutions reached 3,741,120 to produce a powder mixture.

During mixing, the mixing container was hermetically closed with a lidand filled with a gas mixture (Ar+O₂); and under the atmosphere in themixing container, the 50 at % Fe-50 at % Pt alloy powder, the C powder,and the SiO₂ powder were mixed.

When the cumulative number of ball mill revolutions reached 935,280,1,870,560, 2,805,840 and 3,741,120, the mixing container was opened, andwhether or not ignition had occurred was visually checked. However, noignition was found at each point.

When the cumulative number of ball mill revolution reached 3,741,120,30.00 g of the powder mixture was subjected to hot pressing in a vacuumatmosphere at less than 20 Pa to produce a disc-like sintered producthaving a diameter of 30 mm. The hot-pressing conditions (sinteringtemperature, sintering pressure, and sintering time) and the relativedensity of the obtained sintered product are shown in TABLE 11 below.The theoretical density of the sintered product is 11.51 g/cm³, which iscalculated in consideration of a reduction in the amount of carbonduring mixing and sintering (i.e., calculated using the content ofcarbon in the sintered product shown in TABLE 12). Based on thistheoretical density, the relative density of the sintered product wascalculated.

TABLE 11 Cumulative Relative number of Hot-pressure conditions densityof ball mill Sintering Sintering Sintering sintered revolutionstemperature pressure time product (Number) (° C.) (MPa) (min) (%)Ignition 935,280 — — — — NO 1,870,560 — — — — NO 2,805,840 — — — — NO3,741,120 1270 24.5 45 97.31 NO

The relative density of the sintered product exceeds 97%, and the amountof voids in the obtained sintered product was small.

The contents of oxygen and nitrogen in the powder mixture taken at acumulative number of ball mill revolutions of 3,741,120 were measuredusing a TC-600 Series Nitrogen/Oxygen Determinator manufactured by LECOCorporation, and the content of carbon was measured using aCarbon/Sulfur Analyzer manufactured by HORIBA, Ltd. The contents ofoxygen and nitrogen in the sintered product made using the powdermixture taken at a cumulative number of ball mill revolutions of3,741,120 were measured using a TC-600 Series Nitrogen/OxygenDeterminator manufactured by LECO Corporation, and the content of carbonwas measured using a Carbon/Sulfur Analyzer manufactured by HORIBA, Ltd.The measurement results are shown in TABLE 12 below.

TABLE 12 Cumulative number of ball mill revolutions Oxygen NitrogenCarbon of 3,741,120 (mass %) ( mass ppm) (mass %) Powder mixture 1.56130 3.27 Sintered product 1.06 10 2.18

The content of oxygen and the content of nitrogen in the sinteredproduct both decrease compared to those in the powder mixture, while thedegree of reduction in the content of oxygen is smaller than the degreeof reduction in the content of nitrogen. This may be caused by the factthat the powder mixture and the sintered product both contain metaloxide SiO₂.

As comparing the content of oxygen and the content of nitrogen in thesintered product with those in the powder mixture, the degree ofreduction in the content of oxygen and the content of nitrogen due tosintering in Reference Example 5 is larger than that in ReferenceExamples 1 and 2. This may be because the powder mixture of ReferenceExample 5 contains the C powder and thus oxygen and nitrogen have beenadsorbed to the surface of the C powder.

The structure of the sintered product made using the powder mixturetaken at a cumulative number of ball mill revolutions of 3,741,120 wasobserved under a scanning electron microscope (SEM). FIGS. 18 to 21 showSEM photographs of the sintered products. FIG. 18 is a SEM photographtaken at a magnification of 1,000× (a bar scale in the photographrepresents 10 μm). FIG. 19 is a SEM photograph taken at a magnificationof 3,000× (a bar scale in the photograph represents 1 μm). FIG. 20 is aSEM photograph taken at a magnification of 5,000× (a bar scale in thephotograph represents 1 μm). FIG. 21 is a SEM photograph taken at amagnification of 10,000× (a bar scale in the photograph represents 1μm). In FIGS. 18 to 21, black portions correspond to the C phase and theSiO₂ phase, and white portions correspond to the FePt alloy phase. Ascan be seen from FIGS. 18 to 21, fine regions of the C phase and theSiO₂ phase are dispersed in the entire area of the structure.

The average size of the phase consisting of the C phase and the SiO₂phase was determined by the intercept method based on the SEM photographof FIG. 21 taken at a magnification of 10,000×. A specific method is thesame as the method of Reference Example 1. As used herein, the phaseconsisting of the C phase and the SiO₂ phase refers to a phase pickedout as the C phase and the SiO₂ phase, not distinguishing between the Cphase and the SiO₂ phase and regarding them as a same phase.

The results showed that the average size of the phase consisting of theC phase and the SiO₂ phase determined by the intercept method was 0.28μm.

Reference Example 6

The targeted composition of a powder mixture and a target in ReferenceExample 6 is (50Fe-50Pt)-9 vol % C-21 vol % SiO₂. That is, the targetedcomposition of metal components is 50 at % Fe-50 at % Pt; the targetedcontent of C is 9 vol % based on the total amount of the target; and thetargeted content of metal oxide (SiO₂) is 21 vol % based on the totalamount of the target. When the contents of C and metal oxide (SiO₂) arerepresented not by vol % but by mol %, the targeted composition of thepowder mixture and the target in Reference Example 6 is(50Fe-50Pt)-15.24 mol % C-6.92 mol % SiO₂.

To 1100.00 g of 50 at % Fe-50 at % Pt alloy powder produced in the samemanner as in Reference Example 1, 20.57 g of C powder having an averageparticle diameter of 35 μm and a bulk density of 0.25 g/cm³ was added sothat the content of C is 8.8 vol % based on the total amount of thepowders, and 47.73 g of SiO₂ powder having an average particle diameterof 0.7 μm and a bulk density of 2.20 g/cm³ was added so that the contentof SiO₂ was 21.2 vol % based on the total amount of the powders. Thesecomponents were then mixed with a ball mill until the cumulative numberof revolutions reached 3,741,120 to produce a powder mixture.

During mixing, the mixing container was hermetically closed with a lidand filled with a gas mixture (Ar+O₂); and under the atmosphere in themixing container, the 50 at % Fe-50 at % Pt alloy powder, the C powder,and the SiO₂ powder were mixed.

When the cumulative number of ball mill revolutions reached 935,280,1,870,560, 2,805,840 and 3,741,120, the mixing container was opened, andwhether or not ignition had occurred was visually checked. However, noignition was found at each point.

When the cumulative number of ball mill revolution reached 3,741,120,30.00 g of the powder mixture was subjected to hot pressing in a vacuumatmosphere at less than 20 Pa to produce a disc-like sintered producthaving a diameter of 30 mm. The hot-pressing conditions (sinteringtemperature, sintering pressure, and sintering time) and the relativedensity of the obtained sintered product are shown in TABLE 13 below.The theoretical density of the sintered product is 11.51 g/cm³, which iscalculated in consideration of a reduction in the amount of carbonduring mixing and sintering (i.e., calculated using the content ofcarbon in the sintered product shown in TABLE 14). Based on thistheoretical density, the relative density of the sintered product wascalculated.

TABLE 13 Cumulative Relative number of Hot-pressing conditions densityof ball mill Sintering Sintering Sintering sintered revolutionstemperature pressure time product (Number) (° C.) (MPa) (min) (%)Ignition 935,280 — — — — NO 1,870,560 — — — — NO 2,805,840 — — — — NO3,741,120 1280 24.5 45 97.50 NO

The relative density of the sintered product exceeds 97%, and the amountof voids in the obtained sintered product was small.

The contents of oxygen and nitrogen in the powder mixture taken at acumulative number of ball mill revolutions of 3,741,120 were measuredusing a TC-600 Series Nitrogen/Oxygen Determinator manufactured by LECOCorporation, and the content of carbon was measured using aCarbon/Sulfur Analyzer manufactured by HORIBA, Ltd. The contents ofoxygen and nitrogen in the sintered product made using the powdermixture taken at a cumulative number of ball mill revolutions of3,741,120 were measured using a TC-600 Series Nitrogen/OxygenDeterminator manufactured by LECO Corporation, and the content of carbonwas measured using a Carbon/Sulfur Analyzer manufactured by HORIBA, Ltd.The measurement results are shown in TABLE 14 below.

TABLE 14 Cumulative number of ball mill revolutions Oxygen NitrogenCarbon of 3,741,120 (mass %) (mass ppm) (mass %) Powder mixture 3.50 1642.31 Sintered product 1.95 5 1.76

The content of oxygen and the content of nitrogen in the sinteredproduct both decrease compared to those in the powder mixture, while thedegree of reduction in the content of oxygen is smaller than the degreeof reduction in the content of nitrogen. This may be caused by the factthat the powder mixture and the sintered product both contain metaloxide SiO₂.

As comparing the content of oxygen and the content of nitrogen in thesintered product with those in the powder mixture, the degree ofreduction in the content of oxygen and the content of nitrogen due tosintering in Reference Example 6 is larger than that in ReferenceExamples 1 and 2. This may be because the powder mixture of ReferenceExample 6 contains the C powder and thus oxygen and nitrogen have beenadsorbed to the surface of the C powder.

The structure of the sintered product made using the powder mixturetaken at a cumulative number of ball mill revolutions of 3,741,120 wasobserved under a scanning electron microscope (SEM). FIGS. 22 to 25 showSEM photographs of the sintered products. FIG. 22 is a SEM photographtaken at a magnification of 1,000× (a bar scale in the photographrepresents 10 μm). FIG. 23 is a SEM photograph taken at a magnificationof 3,000× (a bar scale in the photograph represents 1 μm). FIG. 24 is aSEM photograph taken at a magnification of 5,000× (a bar scale in thephotograph represents 1 μm). FIG. 25 is a SEM photograph taken at amagnification of 10,000× (a bar scale in the photograph represents 1μm). In FIGS. 22 to 25, black portions correspond to the C phase and theSiO₂ phase, and white portions correspond to the FePt alloy phase. Ascan be seen from FIGS. 22 to 25, fine regions of the C phase and theSiO₂ phase are dispersed in the entire area of the structure.

The average size of the phase consisting of the C phase and the SiO₂phase was determined by the intercept method based on the SEM photographof FIG. 25 taken at a magnification of 10,000×. A specific method is thesame as the method of Reference Example 1. As used herein, the phaseconsisting of the C phase and the SiO₂ phase refers to a phase pickedout as the C phase and the SiO₂ phase, not distinguishing between the Cphase and the SiO₂ phase and regarding them as a same phase.

The results showed that the average size of the phase consisting of theC phase and the SiO₂ phase determined by the intercept method was 0.23μm.

Reference Example 7

The targeted composition of a powder mixture and a target in ReferenceExample 7 is (50Fe-50Pt)-12 vol % C-18 vol % SiO₂. That is, the targetedcomposition of metal components is 50 at % Fe-50 at % Pt; the targetedcontent of C is 12 vol % based on the total amount of the target; andthe targeted content of metal oxide (SiO₂) is 18 vol % based on thetotal amount of the target. When the contents of C and metal oxide(SiO₂) are represented not by vol % but by mol %, the targetedcomposition of the powder mixture and the target in Reference Example 7is (50Fe-50Pt)-19.53 mol % C-5.70 mol % SiO₂.

To 1100.00 g of 50 at % Fe-50 at % Pt alloy powder produced in the samemanner as in Reference Example 1, 27.44 g of C powder having an averageparticle diameter of 35 μm and a bulk density of 0.25 g/cm³ was added sothat the content of C is 12 vol % based on the total amount of thepowders, and 40.07 g of SiO₂ powder having an average particle diameterof 0.7 μm and a bulk density of 2.20 g/cm³ was added so that the contentof SiO₂ was −18 vol % based on the total amount of the powders. Thesecomponents were then mixed with a ball mill until the cumulative numberof revolutions reached 3,741,120 to produce a powder mixture.

During mixing, the mixing container was hermetically closed with a lidand filled with a gas mixture (Ar+O₂); and under the atmosphere in themixing container, the 50 at % Fe-50 at % Pt alloy powder, the C powder,and the SiO₂ powder were mixed.

When the cumulative number of ball mill revolutions reached 935,280,1,870,560, 2,805,840 and 3,741,120, the mixing container was opened, andwhether or not ignition had occurred was visually checked. However, noignition was found at each point.

When the cumulative number of ball mill revolution reached 3,741,120,30.00 g of the powder mixture was subjected to hot pressing in a vacuumatmosphere at less than 20 Pa to produce a disc-like sintered producthaving a diameter of 30 mm. The hot-pressing conditions (sinteringtemperature, sintering pressure, and sintering time) and the relativedensity of the obtained sintered product are shown in TABLE 15 below.The theoretical density of the sintered product is 11.52 g/cm³, which iscalculated in consideration of a reduction in the amount of carbonduring mixing and sintering (i.e., calculated using the content ofcarbon in the sintered product shown in TABLE 16). Based on thistheoretical density, the relative density of the sintered product wascalculated.

TABLE 15 Cumulative Relative number of Hot-pressing conditions densityof ball mill Sintering Sintering Sintering sintered revolutionstemperature pressure time product (Number) (° C.) (MPa) (min) (%)Ignition 935,280 — — — — NO 1,870,560 — — — — NO 2,805,840 — — — — NO3,741,120 1300 24.5 45 96.68 NO

The relative density of the sintered product exceeds 96%, and the amountof voids in the obtained sintered product was small.

The contents of oxygen and nitrogen in the powder mixture taken at acumulative number of ball mill revolutions of 3,741,120 were measuredusing a TC-600 Series Nitrogen/Oxygen Determinator manufactured by LECOCorporation, and the content of carbon was measured using aCarbon/Sulfur Analyzer manufactured by HORIBA, Ltd. The contents ofoxygen and nitrogen in the sintered product made using the powdermixture taken at a cumulative number of ball mill revolutions of3,741,120 were measured using a TC-600 Series Nitrogen/OxygenDeterminator manufactured by LECO Corporation, and the content of carbonwas measured using a Carbon/Sulfur Analyzer manufactured by HORIBA, Ltd.The measurement results are shown in TABLE 16 below.

TABLE 16 Cumulative number of ball mill revolutions Oxygen NitrogenCarbon of 3,741,120 (mass %) mass (ppm) (mass %) Powder mixture 3.26 2093.12 Sintered product 1.79 10 2.47

The content of oxygen and the content of nitrogen in the sinteredproduct both decrease compared to those in the powder mixture, while thedegree of reduction in the content of oxygen is smaller than the degreeof reduction in the content of nitrogen. This may be caused by the factthat the powder mixture and the sintered product both contain metaloxide SiO₂.

As comparing the content of oxygen and the content of nitrogen in thesintered product with those in the powder mixture, the degree ofreduction in the content of oxygen and the content of nitrogen due tosintering in Reference Example 7 is larger than that in ReferenceExamples 1 and 2. This may be because the powder mixture of ReferenceExample 7 contains the C powder and thus oxygen and nitrogen have beenadsorbed to the surface of the C powder.

The structure of the sintered product made using the powder mixturetaken at a cumulative number of ball mill revolutions of 3,741,120 wasobserved under a scanning electron microscope (SEM). FIGS. 26 to 29 showSEM photographs of the sintered products. FIG. 26 is a SEM photographtaken at a magnification of 1,000× (a bar scale in the photographrepresents 10 μm). FIG. 27 is a SEM photograph taken at a magnificationof 3,000× (a bar scale in the photograph represents 1 μm). FIG. 28 is aSEM photograph taken at a magnification of 5,000× (a bar scale in thephotograph represents 1 μm). FIG. 29 is a SEM photograph taken at amagnification of 10,000× (a bar scale in the photograph represents 1μm). In FIGS. 26 to 29, black portions correspond to the C phase and theSiO₂ phase, and white portions correspond to the FePt alloy phase. Ascan be seen from FIGS. 26 to 29, fine regions of the C phase and theSiO₂ phase are dispersed in the entire area of the structure.

The average size of the phase consisting of the C phase and the SiO₂phase was determined by the intercept method based on the SEM photographof FIG. 29 taken at a magnification of 10,000×. A specific method is thesame as the method of Reference Example 1. As used herein, the phaseconsisting of the C phase and the SiO₂ phase refers to a phase pickedout as the C phase and the SiO₂ phase, not distinguishing between the Cphase and the SiO₂ phase and regarding them as a same phase.

The results showed that the average size of the phase consisting of theC phase and the SiO₂ phase determined by the intercept method was 0.30μm.

Reference Example 8

The targeted composition of a powder mixture and a target in ReferenceExample 8 is (50Fe-50Pt)-15 vol % C-15 vol % SiO₂. That is, the targetedcomposition of metal components is 50 at % Fe-50 at % Pt; the targetedcontent of C is 15 vol % based on the total amount of the target; andthe targeted content of metal oxide (SiO₂) is 15 vol % based on thetotal amount of the target. When the contents of C and metal oxide(SiO₂) are represented not by vol % but by mol %, the targetedcomposition of the powder mixture and the target in Reference Example 8is (50Fe-50Pt)-23.48 mol % C-457 mol % SiO₂.

To 1100.00 g of 50 at % Fe-50 at % Pt alloy powder produced in the samemanner as in Reference Example 1, 34.37 g of C powder having an averageparticle diameter of 35 μm and a bulk density of 0.25 g/cm³ was added sothat the content of C is 15 vol % based on the total amount of thepowders, and 33.46 g of SiO₂ powder having an average particle diameterof 0.7 μm and a bulk density of 2.20 g/cm³ was added so that the contentof SiO₂ was 15 vol % based on the total amount of the powders. Thesecomponents were then mixed with a ball mill until the cumulative numberof revolutions reached 3,741,120 to produce a powder mixture.

During mixing, the mixing container was hermetically closed with a lidand filled with a gas mixture (Ar+O₂); and under the atmosphere in themixing container, the 50 at % Fe-50 at % Pt alloy powder, the C powder,and the SiO₂ powder were mixed.

When the cumulative number of ball mill revolutions reached 935,280,1,870,560, 2,805,840 and 3,741,120, the mixing container was opened, andwhether or not ignition had occurred was visually checked. However, noignition was found at each point.

When the cumulative number of ball mill revolution reached 1,870,560,2,805,840 and 3,741,120, 30.00 g of the powder mixture was subjected tohot pressing in a vacuum atmosphere at less than 20 Pa to produce adisc-like sintered product having a diameter of 30 mm. The hot-pressingconditions (sintering temperature, sintering pressure, and sinteringtime) and the relative density of the obtained sintered product areshown in TABLE 17 below. The theoretical density of the sintered productis 11.51 g/cm³, which is calculated in consideration of a reduction inthe amount of carbon during mixing and sintering (i.e., calculated usingthe content of carbon in the sintered product shown in TABLE 18). Basedon this theoretical density, the relative density of the sinteredproduct (sintered product made using the powder mixture taken at acumulative number of ball mill revolutions of 3,741,120) was calculated.

TABLE 17 Cumulative Relative number of Hot-pressing conditions densityof ball mill Sintering Sintering Sintering sintered revolutionstemperature pressure time product (Number) (° C.) (MPa) (min) (%)Ignition 935,280 — — — — NO 1,870,560 1370 26.2 45 — NO 2,805,840 130026.2 45 — NO 3,741,120 1290 26.2 45 95.81 NO

The relative density of the sintered product exceeds 95%, and the amountof voids in the obtained sintered product was small.

The contents of oxygen and nitrogen in the powder mixture taken at acumulative number of ball mill revolutions of 3,741,120 were measuredusing a TC-600 Series Nitrogen/Oxygen Determinator manufactured by LECOCorporation, and the content of carbon was measured using aCarbon/Sulfur Analyzer manufactured by HORIBA, Ltd. The contents ofoxygen and nitrogen in the sintered product made using the powdermixture taken at a cumulative number of ball mill revolutions of3,741,120 were measured using a TC-600 Series Nitrogen/OxygenDeterminator manufactured by LECO Corporation, and the content of carbonwas measured using a Carbon/Sulfur Analyzer manufactured by HORIBA, Ltd.The measurement results are shown in TABLE 18 below.

TABLE 18 Cumulative number of ball Mill revolutions Oxygen NitrogenCarbon of 3,741,120 (mass %) mass (ppm) (mass %) Powder mixture 3.22 1862.87 Sintered product 1.39 6 2.24

The content of oxygen and the content of nitrogen in the sinteredproduct both decrease compared to those in the powder mixture, while thedegree of reduction in the content of oxygen is smaller than the degreeof reduction in the content of nitrogen. This may be caused by the factthat the powder mixture and the sintered product both contain metaloxide SiO₂.

As comparing the content of oxygen and the content of nitrogen in thesintered product with those in the powder mixture, the degree ofreduction in the content of oxygen and the content of nitrogen due tosintering in Reference Example 8 is larger than that in ReferenceExamples 1 and 2. This may be because the powder mixture of ReferenceExample 8 contains the C powder and thus oxygen and nitrogen have beenadsorbed to the surface of the C powder.

The structure of the sintered product made using the powder mixturetaken at a cumulative number of ball mill revolutions of 3,741,120 wasobserved under a scanning electron microscope (SEM). FIGS. 30 to 33 showSEM photographs of the sintered products. FIG. 30 is a SEM photographtaken at a magnification of 1,000× (a bar scale in the photographrepresents 10 μm). FIG. 31 is a SEM photograph taken at a magnificationof 3,000× (a bar scale in the photograph represents 1 μm). FIG. 32 is aSEM photograph taken at a magnification of 5,000× (a bar scale in thephotograph represents 1 μm). FIG. 33 is a SEM photograph taken at amagnification of 10,000× (a bar scale in the photograph represents 1μm). In FIGS. 30 to 33, black portions correspond to the C phase and theSiO₂ phase, and white portions correspond to the FePt alloy phase. Ascan be seen from FIGS. 30 to 33, fine regions of the C phase and theSiO₂ phase are dispersed in the entire area of the structure.

The average size of the phase consisting of the C phase and the SiO₂phase was determined by the intercept method based on the SEM photographof FIG. 33 taken at a magnification of 10,000×. A specific method is thesame as the method of Reference Example 1. As used herein, the phaseconsisting of the C phase and the SiO₂ phase refers to a phase pickedout as the C phase and the SiO₂ phase, not distinguishing between the Cphase and the SiO₂ phase and regarding them as a same phase.

The results showed that the average size of the phase consisting of theC phase and the SiO₂ phase determined by the intercept method was 0.20m.

Reference Example 9

The targeted composition of a powder mixture and a target in ReferenceExample 9 is (50Fe-50Pt)-15 vol % C-15 vol % TiO₂. That is, the targetedcomposition of metal components is 50 at % Fe-50 at % Pt; the targetedcontent of C is 15 vol % based on the total amount of the target; andthe targeted content of metal oxide (TiO₂) is 15 vol % based on thetotal amount of the target. When the contents of C and metal oxide(TiO₂) are represented not by vol % but by mol %, the targetedcomposition of the powder mixture and the target in Reference Example 9is (50Fe-50Pt)-23.04 mol % C-6.39 mol % TiO₂.

To 1100.00 g of 50 at % Fe-50 at % Pt alloy powder produced in the samemanner as in Reference Example 1, 34.38 g of C powder having an averageparticle diameter of 35 μm and a bulk density of 0.25 g/cm³ was added sothat the content of C is 15 vol % based on the total amount of thepowders, and 63.41 g of TiO₂ powder having an average particle diameterof 0.07 μm and a bulk density of 4.11 g/cm³ was added so that thecontent of TiO₂ was 15 vol % based on the total amount of the powders.These components were then mixed with a ball mill until the cumulativenumber of revolutions reached 3,741,120 to produce a powder mixture.

During mixing, the mixing container was hermetically closed with a lidand filled with a gas mixture (Ar+O₂); and under the atmosphere in themixing container, the 50 at % Fe-50 at % Pt alloy powder, the C powder,and the TiO₂ powder were mixed.

When the cumulative number of ball mill revolutions reached 935,280,1,870,560, 2,805,840 and 3,741,120, the mixing container was opened, andwhether or not ignition had occurred was visually checked. However, noignition was found at each point.

When the cumulative number of ball mill revolution reached 1,870,560,2,805,840 and 3,741,120, 30.00 g of the powder mixture was subjected tohot pressing in a vacuum atmosphere at less than 20 Pa to produce adisc-like sintered product having a diameter of 30 mm. The hot-pressingconditions (sintering temperature, sintering pressure, and sinteringtime) and the relative density of the obtained sintered product areshown in TABLE 19 below. The theoretical density of the sintered productis 12.45 g/cm³, which is calculated in consideration of a reduction inthe amount of carbon during mixing and sintering (i.e., calculated usingthe content of carbon in the sintered product shown in TABLE 20). Basedon this theoretical density, the relative density of the sinteredproduct (sintered product made using the powder mixture taken at acumulative number of ball mill revolutions of 3,741,120) was calculated.

TABLE 19 Cumulative Relative number of Hot-pressing conditions densityof ball mill Sintering Sintering Sintering sintered revolutionstemperature pressure time product (Number) (° C.) (MPa) (min) (%)Ignition 935,280 — — — — NO 1,870,560 1350 26.2 45 — NO 2,805,840 129026.2 45 — NO 3,741,120 1280 26.2 45 95.00 NO

The relative density of the sintered product is 95%, and the amount ofvoids in the obtained sintered product was small.

The contents of oxygen and nitrogen in the powder mixture taken at acumulative number of ball mill revolutions of 3,741,120 were measuredusing a TC-600 Series Nitrogen/Oxygen Determinator manufactured by LECOCorporation, and the content of carbon was measured using aCarbon/Sulfur Analyzer manufactured by HORIBA, Ltd. The contents ofoxygen and nitrogen in the sintered product made using the powdermixture taken at a cumulative number of ball mill revolutions of3,741,120 were measured using a TC-600 Series Nitrogen/OxygenDeterminator manufactured by LECO Corporation, and the content of carbonwas measured using a Carbon/Sulfur Analyzer manufactured by HORIBA, Ltd.The measurement results are shown in TABLE 20 below.

TABLE 20 Cumulative number of ball mill revolutions Oxygen NitrogenCarbon of 3,741,120 (mass %) mass (ppm) (mass %) Powder mixture 4.55 1172.72 Sintered product 1.88 5 1.86

The content of oxygen and the content of nitrogen in the sinteredproduct both decrease compared to those in the powder mixture, while thedegree of reduction in the content of oxygen is smaller than the degreeof reduction in the content of nitrogen. This may be caused by the factthat the powder mixture and the sintered product both contain metaloxide TiO₂.

As comparing the content of oxygen and the content of nitrogen in thesintered product with those in the powder mixture, the degree ofreduction in the content of oxygen and the content of nitrogen due tosintering in Reference Example 9 is larger than that in ReferenceExamples 1 and 2. This may be because the powder mixture of ReferenceExample 9 contains the C powder and thus oxygen and nitrogen have beenadsorbed to the surface of the C powder.

The structure of the sintered product made using the powder mixturetaken at a cumulative number of ball mill revolutions of 3,741,120 wasobserved under a scanning electron microscope (SEM). FIGS. 34 to 37 showSEM photographs of the sintered products. FIG. 34 is a SEM photographtaken at a magnification of 1,000× (a bar scale in the photographrepresents 10 μm). FIG. 35 is a SEM photograph taken at a magnificationof 3,000× (a bar scale in the photograph represents 1 μm). FIG. 36 is aSEM photograph taken at a magnification of 5,000× (a bar scale in thephotograph represents 1 μm). FIG. 37 is a SEM photograph taken at amagnification of 10,000× (a bar scale in the photograph represents 1μm). In FIGS. 34 to 37, black portions correspond to the C phase and theTiO₂ phase, and white portions correspond to the FePt alloy phase. Ascan be seen from FIGS. 34 to 37, fine regions of the C phase and theTiO₂ phase are dispersed in the entire area of the structure.

The average size of the phase consisting of the C phase and the SiO₂phase was determined by the intercept method based on the SEM photographof FIG. 37 taken at a magnification of 10,000×. A specific method is thesame as the method of Reference Example 1. As used herein, the phaseconsisting of the C phase and the TiO₂ phase refers to a phase pickedout as the C phase and the TiO₂ phase, not distinguishing between the Cphase and the TiO₂ phase and regarding them as a same phase.

The results showed that the average size of the phase consisting of theC phase and the TiO₂ phase determined by the intercept method was 0.29μm.

Example 1

The targeted composition of a powder mixture and a target in Example 1is (50Fe-45Pt-5Cu)-20.3 vol % B₂O₃. That is, the targeted composition ofmetal components is 50 at % Fe-45 at % Pt-5 at % Cu; and the targetedcontent of metal oxide (B₂O₃) is 20.3 vol % based on the total amount ofthe target. When the content of metal oxide (B₂O₃) is represented not byvol % but by mol %, the targeted composition of the powder mixture andthe target in Example 1 is (50Fe-45Pt-5Cu)-5.1 mol % B₂O₃.

The metals in bulk form were weighed such that the composition of thealloy was Fe: 50 at %, Pt: 45 at %, and Pt: 5 at % and then heated byhigh frequency heating to form a molten Fe—Pt—Cu alloy at 1,800° C. Thena gas atomizing method using argon gas was performed to produce 50 at %Fe-45 at % Pt-5 at % Cu alloy powder. The average particle diameter ofthe obtained alloy powder was measured using Microtrac MT3000manufactured by NIKKISO Co., Ltd. and found to be 50 μm.

To 1030.00 g of the obtained 50 at % Fe-45 at % Pt-5 at % Cu alloypowder, 32.49 g of B₂O₃ powder was added so that the content of B₂O₃ is20.3 vol % based on the total amount of the powders. These componentswere then mixed with a ball mill until the cumulative number ofrevolutions reached 3,852,360 to produce a powder mixture.

During mixing, the mixing container was hermetically closed with a lidand filled with a gas mixture (Ar+O₂); and under the atmosphere in themixing container, the 50 at % Fe-45 at % Pt-5 at % Cu alloy powder andthe B₂O₃ powder were mixed.

When the cumulative number of ball mill revolutions reached 1,046,520,1,981,800, 2,917,080 and 3,852,360, the mixing container was opened, andwhether or not ignition had occurred was visually checked. However, noignition was found at each point.

When the cumulative number of ball mill revolution reached 3,852,360,30.00 g of the powder mixture was subjected to hot pressing in a vacuumatmosphere at less than 20 Pa to produce a disc-like sintered producthaving a diameter of 30 mm. The hot-pressing conditions (sinteringtemperature, sintering pressure, and sintering time) and the relativedensity of the obtained sintered product are shown in TABLE 21 below. Asshown below in TABLE 23, the content of B increased only by 0.04% bymass compared to the state of the powder mixture before sintering in theICP analysis results. Since there was no step involving directincorporation of B₂O₃ in a series of steps including ICP analysis, thetheoretical density of the sintered product was calculated withoutconsideration of an increase in the content of B and found to be 12.22g/cm³. The relative density of the sintered product (sintered productmade using the powder mixture taken at a cumulative number of ball millrevolutions of 3,852,360) was calculated based on the theoreticaldensity of 12.22 g/cm³ and found to be 100.09%.

TABLE 21 Cumulative Relative number of Hot-pressing conditions densityof ball mill Sintering Sintering Sintering sintered revolutionstemperature pressure time product (Number) (° C.) (MPa) (min) (%)Ignition 1,046,520 — — — — NO 1,981,800 — — — — 2,917,080 — — — —3,852,360 770 26.2 45 100.09 NO

The relative density of the sintered product exceeds 100%, and theamount of voids in the obtained sintered product was small.

The contents of oxygen and nitrogen in the sintered product made usingthe powder mixture taken at a cumulative number of ball mill revolutionsof 3,852,360 were measured using a TC-600 Series Nitrogen/OxygenDeterminator manufactured by LECO Corporation. The measurement resultsare shown in TABLE 22 below.

TABLE 22 Cumulative number of ball mill revolutions Oxygen Nitrogen of3,852,360 (mass %) (mass ppm) Sintered product 2.70 58

The contents of Fe, Pt, Cu, and B in the sintered product made of thepowder mixture taken at a cumulative number of ball mill revolutions of3,852,360 were analyzed by ICP. TABLE 25 below shows the analysisresults as well as the contents of Fe, Pt, Cu, and B in the powdermixture before sintering. The contents of Fe, Pt, Cu, and B in thepowder mixture before sintering are not the analysis results by ICP butthe calculated values (theoretical values) based on the amounts of rawmaterial powders blended for producing the powder mixture.

TABLE 23 Cumulative number of ball mill revolutions Fe Pt Cu B of3,852,360 (mass %) (mass %) (mass %) (mass %) Powder mixture 22.77 71.582.59 0.95 Sintered product 22.95 72.73 2.38 0.99

The structure of the sintered product made using the powder mixturetaken at a cumulative number of ball mill revolutions of 3,852,360 wasobserved under a scanning electron microscope (SEM). FIGS. 38 to 41 showSEM photographs of the sintered products. FIG. 38 is a SEM photographtaken at a magnification of 1,000× (a bar scale in the photographrepresents 10 μm). FIG. 39 is a SEM photograph taken at a magnificationof 3,000× (a bar scale in the photograph represents 1 μm). FIG. 40 is aSEM photograph taken at a magnification of 5,000× (a bar scale in thephotograph represents 1 μm). FIG. 41 is a SEM photograph taken at amagnification of 10,000× (a bar scale in the photograph represents 1μm). In FIGS. 38 to 41, black portions correspond to the B₂O₃ phase, andwhite portions correspond to the FePtCu alloy phase. As can be seen fromFIGS. 38 to 41, fine regions of the B₂O₃ phase are dispersed in theentire area of the structure.

The average size of the B₂O₃ phase was determined by the interceptmethod based on the SEM photograph of FIG. 41 taken at a magnificationof 10,000×. A specific method is the same as the method of ReferenceExample 1.

The results showed that the average size of the B₂O₃ phase determined bythe intercept method was 0.14 μm.

Example 2

The targeted composition of a powder mixture and a target in Example 2is (45Fe-45Pt-10Cu)-15 vol % C-15 vol % SiO₂. That is, the targetedcomposition of metal components is 45 at % Fe-45 at % Pt-10 at % Cu; thetargeted content of C is 15 vol % based on the total amount of thetarget; and the targeted content of metal oxide (SiO₂) is 15 vol % basedon the total amount of the target. When the contents of C and metaloxide (SiO₂) are represented not by vol % but by mol %, the targetedcomposition of the powder mixture and the target in Example 2 is(45Fe-45Pt-10Cu)-24 mol %/C-5 mol % SiO₂.

The metals in bulk form were weighed such that the composition of thealloy was Fe: 45 at %, Pt: 45 at %, and Cu: 10 at % and then heated byhigh frequency heating to form a molten Fe—Pt—Cu alloy at 1,800° C. Thena gas atomizing method using argon gas was performed to produce 45 at %Fe-45 at % Pt-10 at % Cu alloy powder. The average particle diameter ofthe obtained alloy powder was measured using Microtrac MT3000manufactured by NIKKISO Co., Ltd. and found to be 50 μm.

To 1020.00 g of the obtained 45 at % Fe-45 at % Pt-10 at % Cu alloypowder, 44.63 g of C powder having an average particle diameter of 35 μmand a bulk density of 0.25 g/cm³ was added so that the content of C is15 vol % based on the total amount of the powders, and 32.56 g of SiO₂powder having an average particle diameter of 0.7 μm and a bulk densityof 2.20 g/cm³ was added so that the content of SiO₂ was 15 vol % basedon the total amount of the powders. These components were then mixedwith a ball mill until the cumulative number of revolutions reached5,736,960 to produce a powder mixture.

During mixing, the mixing container was hermetically closed with a lidand filled with a gas mixture (Ar+O₂); and under the atmosphere in themixing container, the 45 at % Fe-45 at % Pt-10 at % Cu alloy powder, theC powder, and the SiO₂ powder were mixed.

When the cumulative number of ball mill revolutions reached 935,280,2,535,840), 4,136,400 and 5,736,960, the mixing container was opened,and whether or not ignition had occurred was visually checked. However,no ignition was found at each point.

When the cumulative number of ball mill revolution reached 5,736,960,30.00 g of the powder mixture was subjected to hot pressing in a vacuumatmosphere at less than 20 Pa to produce a disc-like sintered producthaving a diameter of 30 mm. The hot-pressing conditions (sinteringtemperature, sintering pressure, and sintering time) and the relativedensity of the obtained sintered product are shown in TABLE 24 below.The theoretical density of the sintered product is 11.11 g/cm³, which iscalculated in consideration of a reduction in the amount of carbonduring mixing and sintering (i.e., calculated using the content ofcarbon in the sintered product shown in TABLE 25). Based on thistheoretical density, the relative density of the sintered product(sintered product made using the powder mixture taken at a cumulativenumber of ball mill revolutions of 5,736,960) was calculated.

TABLE 24 Cumulative Relative number of Hot-pressing conditions densityof ball mill Sintering Sintering Sintering sintered revolutionstemperature pressure time product (Number) (° C.) (MPa) (min) (%)Ignition 935,280 — — — — NO 2,535,840 — — — — NO 4,136,400 — — — — NO5,736,960 1420 24.5 45 93.36 NO

The relative density of the sintered product exceeds 93%, and the amountof voids in the obtained sintered product was small.

The contents of oxygen and nitrogen in the sintered product made usingthe powder mixture taken at a cumulative number of ball mill revolutionsof 5,736,960 were measured using a TC-600 Series Nitrogen/OxygenDeterminator manufactured by LECO Corporation, and the content of carbonwas measured using a Carbon/Sulfur Analyzer manufactured by HORIBA, Ltd.The measurement results are shown in TABLE 25 below.

TABLE 25 Cumulative number of ball mill revolutions Oxygen NitrogenCarbon of 5,736,960 (mass %) (mass ppm) (mass %) Sintered product 1.4623 3.30

The structure of the sintered product made using the powder mixturetaken at a cumulative number of ball mill revolutions of 5,736,960 wasobserved under a scanning electron microscope (SEM). FIGS. 42 to 44 showSEM photographs of the sintered products. FIG. 42 is a SEM photographtaken at a magnification of 3,000× (a bar scale in the photographrepresents 1 μm). FIG. 43 is a SEM photograph taken at a magnificationof 5,000× (a bar scale in the photograph represents 1 μm). FIG. 44 is aSEM photograph taken at a magnification of 10,000× (a bar scale in thephotograph represents 1 μm). In FIGS. 42 to 44, black portionscorrespond to the C phase and the TiO₂ phase, and white portionscorrespond to the FePtCu alloy phase. As can be seen from FIGS. 42 to44, fine regions of the C phase and the SiO₂ phase are dispersed in theentire area of the structure.

The average size of the phase consisting of the C phase and the SiO₂phase was determined by the intercept method based on the SEM photographof FIG. 44 taken at a magnification of 10,000×. A specific method is thesame as the method of Reference Example 1. As used herein, the phaseconsisting of the C phase and the SiO₂ phase refers to a phase pickedout as the C phase and the SiO₂ phase, not distinguishing between the Cphase and the SiO₂ phase and regarding them as a same phase.

The results showed that the average size of the phase consisting of theC phase and the SiO₂ phase determined by the intercept method was 0.27μm.

Comparative Example 1

The targeted composition of a powder mixture and a target in Comparativeexample 1 is (50Fe-50Pt)-30 vol % C. More specifically, the targetedcomposition of the metal components is 50 at % Fe-50 at % Pt, and thetargeted content of C is 30 vol % based on the total amount of thetarget. When the content of C is represented not by vol % but by at %,the targeted composition of the powder mixture and the target inComparative example 1 is (50Fe-50Pt)-40 at % C.

A powder mixture and a sintered product were produced in the same manneras in Reference Example 1 except that C powder was used instead of SiO₂powder, that a mixing container was filled with argon (Ar) andhermetically sealed, and FePt powder and C powder were mixed in thesealed mixing container, that the cumulative number of ball millrevolutions was changed, that the number of times and the timing ofintroduction of fresh air by opening the mixing container during mixingwere changed, and that the sintering temperature during the productionof the sintered product was changed to 1,100° C.

When the cumulative number of ball mill revolutions reached 209,520,608,040, 1,006,560, 1,405,080, 1,803,600, 2,202,120, and 2,816,640, themixing container was opened, and whether or not ignition had occurredwas visually checked. Until the point of time when the cumulative numberof ball mill revolutions was 2,202,120, no ignition was found. However,at the point of time when the cumulative number of ball mill revolutionswas 2,816,640, ignition was found.

To be precise, the atmosphere in the mixing container during mixing wasthe sealed gas mixture (Ar—O₂) atmosphere only in the initial stage ofmixing (until the cumulative number of ball mill revolutions reached209,520) and was a sealed argon (Ar) atmosphere thereafter. The mixingwas performed in the sealed gas mixture (Ar—O₂) atmosphere only in theinitial stage of mixing (until the cumulative number of ball millrevolutions reached 209,520). This cumulative number of ball millrevolutions is only 7.4% of the final cumulative number of ball millrevolutions, i.e., 2,816,640, so that the amount of oxygen adsorbed onthe surface of the C powder in the initial stage of mixing (until thecumulative number of ball mill revolutions reached 209,520) isconsidered to be small. Therefore, Comparative Example 1 is thought tobe an experimental example in which the FePt powder and the C particleshaving a certain amount or less of oxygen adsorbed thereon are mixed2,816,640−209,520=2,607,120 times in the argon (Ar) atmosphere.

30.00 g of the powder mixture mixed until the cumulative number of ballmill revolutions reached 1,405,080 was subjected to hot pressing underthe conditions of temperature: 1,100° C., pressure: 25 MPa, time: 45min., atmosphere: a vacuum of 5×10⁻² Pa or lower to thereby produce adisc-like sintered product having a diameter of 30 mm.

The density of each of the produced sintered products was measured bythe Archimedes method, and the measured value was divided by atheoretical density to determine the relative density. The results areshown in TABLE 26 below. In Comparative Example 1, the theoreticaldensity was not computed in consideration of a reduction in the amountof carbon during sintering, as was in Reference Examples 5 to 9 andExample 2.

TABLE 26 Sintering Theoretical Relative Sintered powder temperatureDensity density density mixture (° C.) (g/cm³) (g/cm³) (%) Powdermixture when 1,100 8.16 11.47 71.1 cumulative number of ball millrevolutions was 1,810,080

The relative density of the sintered product was low, i.e., 71.1%, sothat the sintered product contained a large amount of voids. If therelative density is computed using the theoretical density computed inconsideration of a reduction in the amount of carbon during sintering,the relative density in Comparative Example 1 may be much smaller than71.1%.

(Discussion)

The principal experimental data in Reference Examples 1 to 9 andExamples 1 to 2, and Comparative Example 1 is summarized in TABLE 27below. In TABLE 27, the average size of the phase means the average sizeof the metal oxide phase in Reference Examples 1 to 4 and Example 1, ormeans the average size of the phase consisting of the C phase and themetal oxide phase in Reference Examples 5 to 9 and Example 2.

TABLE 27 Cumulative number of Average Atmosphere ball mill SinteringRelative size of during revolutions temperature density phaseComposition of target mixing (Number) (° C.) (%) (μm) Ignition Reference(50Fe—50Pt)—30 vol % SiO₂ Ar + O₂ 3,741,120 1050 98.61 0.34 NO example 1Reference (50Fe—50Pt)—30 vol % TiO₂ Ar + O₂ 3,741,120 950 96.69 0.28 NOexample 2 Reference (50Fe—50Pt)—36.63 vol % B₂O₃ Ar + O₂ 5,736,960 840105.22 0.22 NO example 3 Reference (50Fe—50Pt)—12.07 vol % B₂O₃—24.68vol Ar + O₂ 3,852,360 830 100.38 0.27 NO example 4 % SiO₂ Reference(50Fe—50Pt)—6 vol % C—24 vol % SiO₂ Ar + O₂ 3,741,120 1270 97.31 0.28 NOexample 5 Reference (50Fe—50Pt)—9 vol % C—21 vol % SiO₂ Ar + O₂3,741,120 1280 97.50 0.23 NO example 6 Reference (50Fe—50Pt)—12 vol %C—18 vol % SiO₂ Ar + O₂ 3,741,120 1300 96.68 0.3 NO example 7 Reference(50Fe—50Pt)—15 vol % C—15 vol % SiO₂ Ar + O₂ 3,741,120 1290 95.81 0.2 NOexample 8 Reference (50Fe—50Pt)—15 vol % C—15 vol % TiO₂ Ar + O₂3,741,120 1280 95.00 0.29 NO example 9 example 1 (50Fe—45Pt—5Cu)—20.3vol % B₂O₃ Ar + O₂ 3,852,360 770 100.09 0.14 NO example 2(45Fe—45Pt—10Cu)—15 vol % C—15 vol % SiO₂ Ar + O₂ 5,736,960 1420 93.360.27 NO Comparative (50Fe—50Pt)—30 vol % C Ar 1,405,080 1100 71.10 — NOexample 1 2,816,640 — — — Yes

In Reference Examples 1 to 9 and Examples 1 to 2, no ignition was foundeven after the cumulative number of ball mill revolutions reached3,000,000.

In Reference Examples 1 to 9 and Examples 1 to 2, Fe is alloyed with Ptto form FePt alloy powder; in Reference Examples 5 and 6, Fe is alloyedwith Pt and Cu to form FePtCu alloy powder. This can reduce the activityof Fe even in the form of powder, thereby suppressing oxidation andignition of Fe during mixing with the metal oxide powder or duringmixing with the metal oxide powder and the C powder.

In Reference Examples 5 to 9 and Example 2, the powder mixture containsC powder. Since the atmosphere during the production of the powdermixture is a gas mixture (Ar+O₂), i.e., the atmosphere contains oxygen,a certain amount of oxygen is adsorbed to the surface of the C powderduring mixing. Therefore, a certain amount of oxygen has already beenadsorbed to the surface of C particles, and accordingly rapid adsorptionof oxygen to the surface of the C particles and subsequent ignition ofthe C particles hardly occur even when the mixing container is opened tointroduce the air after mixing, thereby allowing stable production evenof the FePt-based sputtering target containing not only the metal oxidebut also C.

However, in Reference Example 1 in which the FePt powder and the Cpowder were mixed in an argon atmosphere containing no oxygen during aperiod from when the cumulative number of ball mill revolutions was209,521 to when it reached 2,816,640, ignition was found when the mixingcontainer was opened at the point of time when the cumulative number ofball mill revolutions was 2,816,640. In Reference Example 1, this may becaused by mixing of the FePt powder and the C powder in an argonatmosphere containing no oxygen during a period from when the cumulativenumber of ball mill revolutions was 209,521 to when it reached2,816,640, and by the content of the C powder as large as 30 vol %.

In Reference Examples 1 to 9 and Examples 1 to 2, the cumulative numberof ball mill revolutions was 3,000,000 or more, i.e., in ReferenceExamples 1 to 9 and Examples 1 to 2, the powder mixtures were producedby sufficient mixing. Therefore, in Reference Examples 1 to 9 andExamples 1 to 2, the metal oxide powder and the C powder in the powdermixtures became small enough. Accordingly, this may allow, in thesintered products produced in Reference Examples 1 to 9 and Examples 1to 2, the size of the metal oxide phase, or the average size of thephase consisting of the C phase and the SiO₂ phase, as measured by theintercept method, to be as small as 0.14 to 0.34 μm. Also this may allowthe obtained sintered products to have a relative density as large as90% or more.

In Comparative Example 1, the sintered product was produced using thepowder mixture mixed until the cumulative number of ball millrevolutions reached 1,405,080, but the relative density of the producedsintered product was as small as 71.1%. One reason for this may be theinfluence of low sintering temperature, 1,100° C., in ReferenceExample 1. Another reason may be that, since the cumulative number ofball mill revolutions was small, the particle diameter of the C powderin the powder mixture used to produce the sintered product was notsufficiently reduced, so that voids in the sintered product became largeand the relative density of the sintered product became small.

INDUSTRIAL APPLICABILITY

The target according to the present invention can be preferably used asan FePt-based sputtering target. The production process according to thepresent invention can be preferably used as a process for producing anFePt-based sputtering target.

REFERENCE SIGNS LIST

-   -   10 Substrate    -   10A Substrate surface    -   12 FePt alloy particles    -   14 Carbon phase

The invention claimed is:
 1. An FePt-based sputtering target comprisingFe, Pt, a metal oxide, and further comprising one or more kinds of metalelements other than Fe and Pt, wherein the FePt-based sputtering targethas a structure in which an FePt-based alloy phase and a metal oxidephase containing unavoidable impurities are mutually dispersed, theFePt-based alloy phase containing Pt in an amount of 40 at % or more andless than 60 at % and the one or more kinds of metal elements other thanFe and Pt in an amount of more than 0 at % and 20 at % or less with thebalance being Fe and unavoidable impurities and with a total amount ofPt and the one or more kinds of metal elements being 60 at % or less,the metal oxide is contained in an amount of 20 vol % or more and 40 vol% or less based on a total amount of the target, and the metal oxidephase has an average size of 0.4 μm or less as determined by anintercept method.
 2. An FePt-based sputtering target comprising Fe, Pt,C, a metal oxide, and further comprising one or more kinds of metalelements other than Fe and Pt, wherein the FePt-based sputtering targethas a structure in which an FePt-based alloy phase, a C phase containingunavoidable impurities, and a metal oxide phase containing unavoidableimpurities are mutually dispersed, the FePt-based alloy phase containingPt in an amount of 40 at % or more and less than 60 at % and the one ormore kinds of metal elements other than Fe and Pt in an amount of morethan 0 at % and 20 at % or less with the balance being Fe andunavoidable impurities and with a total amount of Pt and the one or morekinds of metal elements being 60 at % or less, C is contained in anamount of more than 0 vol % and 20 vol % or less based on a total amountof the target, the metal oxide is contained in an amount of 10 vol % ormore and less than 40 vol % based on the total amount of the target, anda total content of C and the metal oxide is 20 vol % or more and 40 vol% or less based on the total amount of the target, and a phaseconsisting of the C phase and the metal oxide phase has an average sizeof 0.4 μm or less as determined by an intercept method.
 3. TheFePt-based sputtering target according to claim 1, wherein the one ormore kinds of metal elements other than Fe and Pt are one or more kindsof Cu, Ag, Mn, Ni, Co, Pd, Cr, V, and B.
 4. The FePt-based sputteringtarget according to claim 2, wherein the one or more kinds of metalelements other than Fe and Pt are one or more kinds of Cu, Ag, Mn, Ni,Co, Pd, Cr, V, and B.
 5. The FePt-based sputtering target according toclaim 1, wherein the one or more kinds of metal elements other than Feand Pt include Cu.
 6. The FePt-based sputtering target according toclaim 2, wherein the one or more kinds of metal elements other than Feand Pt include Cu.
 7. The FePt-based sputtering target according toclaim 1, wherein the one or more kinds of metal elements other than Feand Pt are only Cu.
 8. The FePt-based sputtering target according toclaim 2, wherein the one or more kinds of metal elements other than Feand Pt are only Cu.
 9. The FePt-based sputtering target according toclaim 1, wherein the metal oxide contains at least one of SiO₂, TiO₂,Ti₂O₃, Ta₂O₅, Cr₂O₃, CoO, Co₃O₄, B₂O₃, Fe₂O₃, CuO, Cu₂O, Y₂O₃, MgO,Al₂O₃, ZrO₂, Nb₂O₅, MoO₃, CeO₂, Sm₂O₃, Gd₂O₃, WO₂, WO₃, HfO₂, and NiO₂.10. The FePt-based sputtering target according to claim 2, wherein themetal oxide contains at least one of SiO₂, TiO₂, Ti₂O₃, Ta₂O₅, Cr₂O₃,CoO, Co₃O₄, B₂O₃, Fe₂O₃, CuO, Cu₂O, Y₂O₃, MgO, Al₂O₃, ZrO₂, Nb₂O₅, MoO₃,CeO₂, Sm₂O₃, Gd₂O₃, WO₂, WO₃, HfO₂, and NiO₂.
 11. The FePt-basedsputtering target according to claim 1, wherein the FePt-basedsputtering target has a relative density of 90% or higher.
 12. TheFePt-based sputtering target according to claim 2, wherein theFePt-based sputtering target has a relative density of 90% or higher.13. The FePt-based sputtering target according to claim 1, wherein theFePt-based sputtering target is used for a magnetic recording medium.14. The FePt-based sputtering target according to claim 2, wherein theFePt-based sputtering target is used for a magnetic recording medium.15. The FePt-based sputtering target according to claim 1, wherein themetal oxide is contained in an amount more than 30 vol % and 40 vol % orless based on a total amount of the target.
 16. The FePt-basedsputtering target according to claim 2, wherein the metal oxide iscontained in an amount more than 30 vol % and 40 vol % or less based ona total amount of the target.
 17. The FePt-based sputtering targetaccording to claim 1, wherein the metal oxide contains one or more metaloxides selected from the group consisting of CoO, Co₃O₄, Fe₂O₃, CuO,Cu₂O, Y₂O₃, MoO₃, CeO₂, Sm₂O₃, and Gd₂O₃.
 18. The FePt-based sputteringtarget according to claim 2, wherein the metal oxide contains one ormore metal oxides selected from the group consisting of CoO, Co₃O₄,Fe₂O₃, CuO, Cu₂O, Y₂O₃, MoO₃, CeO₂, Sm₂O₃, and Gd₂O₃.